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Leukemia - Acute

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Revised: 7 November 2014
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.


General


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 23 December 2011, last major update December 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
=========================================================================

● “Acute” because cells are immature (usually blasts) compared to mature hematopoietic cells in chronic leukemias
● Acute leukemias also tend to progress rapidly without treatment, compared to indolent behavior of chronic leukemias

Clinical features
=========================================================================

● Ionizing radiation is only definite environmental risk factor (Environ Health Perspect 2007;115:138)
● Course of disease not affected by pregnancy (Cancer 2005;104:110)
● Initial diagnosis usually based on blood counts and blood smear
● Bone marrow examination (biopsy and smears) is necessary to confirm diagnosis and to obtain material for special studies
● Bone marrow biopsy is essential to assess cellularity extent of involvement and to monitor post-treatment changes
● Cytogenetics and molecular studies are required to classify and provide prognostic information
● Before making a diagnosis, review clinical information, all pathology material and special studies
● Immunostains should be ordered in panels (with multiple antigens) since aberrant antigen expression is common
Common lymphoid immunostains: TdT, T cell - CD2, CD3 (cytoplasmic), CD5, CD7; B cell - HLA-DR, CD10, CD19, CD22, CD79a (cytoplasmic), PAX5, CD20 (tissue sections)
Common myeloid immunostains: CD13, CD14, CD15, CD33, CD36, CD61, CD64

Post-treatment:
● Initially hypocellular with necrosis, proteinaceous debris, dilated sinuses and increased reticulin
● Regeneration begins after 1-2 weeks
● May be difficult to differentiate residual disease (tumor cells in no specific locations) from regenerating marrow (promyelocytes are perivascular and endosteal), particularly in acute promyelocytic leukemia
● May have granulomas associated with microorganisms

Micro description
=========================================================================

● Bone marrow usually markedly hypercellular with replacement of normal cells by myeloblasts
● Myelofibrosis relatively common
● Marrow is rarely hypocellular resembling aplastic anemia, but most cells are blasts



Acute myeloid leukemia (AML) - general


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 23 December 2011, last major update December 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
=========================================================================

● Also called acute myelogenous leukemia
● Clonal neoplastic proliferation of hematopoietic precursor cells, causing excessive myeloblasts and other immature myeloid cells

Clinical features
=========================================================================

● Malignant cells replace bone marrow, may infiltrate spleen, liver and lymph nodes and circulate in bloodstream
● Usually less nodal involvement than ALL
● 80% of adult leukemias but only 20% of childhood leukemias
● Neoplastic blasts have normal proliferation rates but reduced maturation rates compared to normal blasts

Risk factors:
● Most patients have none
● Drugs (alkylating agents, Topoisomerase II inhibition, antimetabolites, antitubulin agents), radiation therapy
● Down’s syndrome
● Bloom’s syndrome
● Fanconi’s anemia
● Neurofibromatosis
● Benzene exposure

Symptoms:
● Due to replacement of normal bone marrow cells by blasts
● Fatigue (due to anemia)
● Fever and opportunistic infections (due to neutropenia)
● Mucosal and cutaneous bleeding (due to thrombocytopenia)
● Tissue infiltration with myelomonocytic, monocytic and monoblastic leukemia, including gingival hyperplasia and leukemia cutis (monocytes tend to infiltrate)
● Sternal tenderness (due to bone marrow expansion)
● Neurological symptoms (due to CNS infiltration)

Laboratory:
● 50% have WBC > 10,000, 20% have WBC > 100,000
● Due to circulating blasts and other immature myeloid cells
● In aleukemic leukemia, peripheral blood lacks blasts, and must examine bone marrow

Diagnosis:
● Examination of blood, marrow smears and cytochemical stains is usually sufficient
● Immunostains may be required for poorly differentiated leukemia

Prognostic features
=========================================================================

Favorable Prognostic Factors:
● Young patients
● Rapid response to chemotherapy
● Favorable cytogenetics - see below

Unfavorable Prognostic Factors:
● Under age 2 or older than age 60
● Marked leukocytosis at diagnosis
● History of myelodysplastic syndrome
● FLT3 mutations (Blood 2006;108:3654, Blood 2002;99:4326)

Treatment
=========================================================================

● Chemotherapy cures 10-30% (induction, consolidation, maintenance phases)
● Allogeneic bone marrow transplantation cures 45-65%
● 5 year survival only 20% in adults, 50% in children (Oncologist 2007;12:341)

Micro description
=========================================================================

Peripheral smear:
● Anisopoikilocytosis (variation in size and shape of red blood cells)
● Nucleated red cells
● Neutropenia
● Thrombocytopenia
● Hypogranular and hyposegmented neutrophils
● Large atypical platelets

Aspirate Micro-Smears:
● Myeloblasts are usually larger than lymphoblasts of ALL
● Cytoplasm is more abundant, with fine azurophilic granules and Auer rods (abnormal crystallized azurophilic granules, particularly in promyelocytic leukemia)
● Delicate nuclear chromatin with 1-4 prominent nucleoli
● Often dysplastic, maturing myeloid cells

Micro-biopsy:
● Usually markedly hypercellular with immature appearing cells but no trilinear maturation
● By definition, at least 20% blasts
● Mitotic activity common
● May have myelofibrosis(though uncommon)
● See also descriptions of various AML subtypes
Type I myeloblasts: no cytoplasmic granules; nucleus is large with delicate chromatin and prominent nucleolus
Type II myeloblasts: 15-20 delicate cytoplasmic granules
Type III myeloblasts: >15-20 cytoplasmic granules, but otherwise has features of a blast cell

Micro images
=========================================================================



Two myeloblasts each have a single prominent Auer rod


Auer rod in neutrophil

Molecular / cytogenetics description
=========================================================================

● 90% have chromosomal abnormalities
● De novo leukemia often has balanced translocations, but therapy related or post-myelodysplasia leukemia often has deletions or monosomy 5 or 7 without translocations

Favorable Cytogenetics:
● inv(16)(p13;q22), t(8;21)(q22;q22), t(15;17)(q22;q12)

Intermediate Cytogenetics:
● +8, t(6;9)(p23;q34), t(9;11)(p22;q23) in children
● Normal cytogenetics

Unfavorable Cytogenetics:
● -7, -5, del 7q, t(11q23), inv(3q), t(9;22)
● Complex abnormalities
● Post-chemotherapy or post-radiation therapy

Positive stains
=========================================================================

● Myeloid markers (CD13, CD14, CD15, CD33, CD36)
● CD99 (43% of AML, 55% of chloromas, Mod Pathol 2000;13:452)
● Often expresses B cell antigens CD20, CD7, PAX5, OCT2 or BOB.1 (Am J Clin Pathol 2006;126:916)
● VEGF expression varies by subtype (Am J Clin Pathol 2003;119:663)

Positive enzyme cytochemistry:
=========================================================================

● Myeloperoxidase (Mod Pathol 1991;4:733), Sudan Black B, chloroacetate esterase (stains lysosomes in granulocytes)
● Variable for acid phosphatase
● M4/M5 are positive for nonspecific esterase (alpha naphthyl butyrate esterase)
● M5/M6/M7 are positive for PAS
Alpha-naphthyl acetate esterase (ANAE): also called modified nonspecific esterase; stains some T cells (Klin Lab Diagn 1993;6:38) and monocytic cells (Leuk Res 1998;22:25), but not erythroid cells
Alpha-naphthyl butyrate esterase: also called nonspecific esterase; stains monocytes and some T cells (J Exp Med 1981;153:182)
Chloroacetate esterase: also called specific esterase, naphthol AS-D chloroacetate esterase, Leder stain; stains granulocytes and mast cells, but not monocytes or lymphocytes

Negative stains
=========================================================================

● CD10

Flow cytometry description
=========================================================================

Immunohistochemmistry compared with flow cytometry:
● CD34 has similar findings
● CD15 and CD117 are more sensitive by flow
● Myeloperoxidase is more sensitive by immunohistochemistry (Arch Pathol Lab Med 2001;125:1063)

Differential diagnosis
=========================================================================

● Reactive process: growth factor treatment causes increased blasts
● Transient myeloproliferative disorder of newborns: resembles AML-M7, ALL, myelodysplastic syndrome

Additional references
=========================================================================

eMedicine, Wikipedia, US National Cancer Institute



AML

Classification


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 27 December 2011, last major update December 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
=========================================================================

● French-American-British (FAB) classification system was used from 1976 to 2001, divided AML into M0-M7 (Br J Haematol 1976;33:451)
● WHO classification (2001 and revised in 2008) requires minimium of 20% of blasts in bone marrow or blood to diagnose AML (was 30% under FAB), which eliminates myelodysplastic category of “refractory anemia with excess blasts in transformation” (Blood 2002;100:2292)
● WHO classification also separates out AML “with recurrent genetic abnormalities”, which have distinct clinical features

Acute myeloid leukemias with recurrent genetic abnormalities:
● AML with t(8;21)(q22;q22); RUNX1-RUNX1T1
● AML with inv(16)(p13.1;q22) or t(16;16)(p13.1;q22); CBF&beta-MYH11
● Acute promyelocytic leukemia with t(15;17)(q22;q12); PML/RAR&alpha and variants
● AML with t(9;11)(p22;q23); MLLT3-MLL
● AML with t(6;9)(p23;q34); DEK-NUP214
● AML with inv(3)(q21q26.2) or t(3;3)(q21;q26.2); RPN1-EVI1
● AML (megakaryoblastic) with t(1;22)(p13;q13); RBM15-MKL1
● AML with mutated NPM1*
● AML with mutated CEBPA*

* provisional

Acute myeloid leukemia with myelodysplasia related changes

Therapy related acute myeloid leukemia
● Alkylating agent related
● Topoisomerase II inhibitor related (some maybe lymphoid)

Acute myeloid leukemia not otherwise categorized:
● AML minimally differentiated (M0)
● AML without maturation (M1)
● AML with maturation (M2)
● Acute myelomonocytic leukemia (M4)
● Acute monoblastic and monocytic leukemia (M5a, M5b)
● Acute erythroid leukemia (M6)
● Acute megakaryoblastic leukemia (M7)
● Acute basophilic leukemia
● Acute panmyelosis with myelofibrosis

Myeloid Sarcoma

Myeloid proliferations related to Down syndrome:
● Transient abnormal myelopoeisis
● Myeloid leukemia associated with Down syndrome

Blastic plasmacytoid dentritic cell neoplasm:

Acute leukemia of ambiguous lineage:
● Acute undifferentiated leukemia
● Mixed phenotype acute leukemia with t(9;22)(q34;q11.2); BCR-ABL1
● Mixed phenotype acute leukemia with t(v;11q23); MLL rearranged
● Mixed phenotype acute leukemia, B/myeloid, NOS
● Mixed phenotype acute leukemia, T/myeloid, NOS
● Mixed phenotype acute leukemia, NOS, rare types
● Other acute leukemia of ambiguous lineage

References: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue (IARC, 2008), Discovery Medicine 2010, eMedicine



AML not otherwise categorized

Transient abnormal myelopoiesis (TAM)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Myeloid proliferations related to Down syndrome (trisomy 21) include transient abnormal myelopoiesis (TAM) and Myeloid leukemia associated with Down syndrome; separate categories in WHO 2008
● TAM occurs in 10% of Down syndrome newborns, clinical and morphologic findings indistinguishable from AML
● Blasts morphologically and immunophenotypically are similar to megakaryocytic lineage
● Down syndrome patients have increased risk for AML, usually AMKL (AML M7)
● TAM usually resolves in 2-14 weeks in neonates, but 20-30% progress to AMKL within 3 years
● TAM: early death in 17%, associated with high white blood cells at diagnosis, increased bilirubin and liver enzymes and failure to normalize white blood cells (Blood 2006;107:4606)
● TAM rarely occurs without Down syndrome (Arch Dis Child Fetal Neonatal Ed 1998;79:F215)

Clinical features
=========================================================================

● 10% of newborns with Down syndrome, but uncommon in neonates with trisomy 21 mosaicism
● Thrombocytopenia, marked leucocytosis, %blasts in peripheral blood may exceed %blasts in bone marrow; also hepatosplenomegaly, cardiopulmonary failure, hyperviscosity, splenic necrosis and progressive hepatic fibrosis

Case reports
=========================================================================

● Stillborn male fetus, gestational age 28 weeks, with severe disease (Nat Clin Pract Oncol 2007;4:433)
● Newborn (Hum Pathol 2000;31:396)

Treatment
=========================================================================

● Less intensive chemotherapy may be effective (J Clin Oncol 2007;25:5442)

Micro description
=========================================================================

● Blasts have moderate basophilic cytoplasm with cytoplasmic blebs, coarse azurophilic granules resembling those in basophils, round to slightly irregular nuclei
● Also promegakaryocytes, micromegakaryocytes and dyserythropoiesis
Peripheral blood: White blood cells up to 100K with 30-50% blasts, nucleated red blood cells and micromegakaryocytes

Micro images
=========================================================================



Blasts in transient abnormal myelopoiesis of Down syndrome

Positive stains
=========================================================================

● CD4 (dim), CD7, CD13, CD33, CD34, CD36, CD41, CD42, CD56, CD61, CD71, CD117, TPO-R, IL-3R, HLA-DR (30%) (Am J Clin Pathol 2001;116:204)

Negative stains
=========================================================================

● CD11b, CD13, CD14, CD15, glycophorin A, myeloperoxidase and Sudan Black B

Molecular description
=========================================================================

● Trisomy 21 and acquired mutations in GATA1 gene in almost all cases (versus 4% of all Down syndrome infants, Blood 2007;110:2128), specific mutations may differ in TAM and subsequent AMKL (Int J Hematol 2007;86:250)
● Loss of GATA1 impairs maturation of megakaryocyte erythroid progenitors (Blood 2006;107:87)
● JAK3 mutations in 50% (Br J Haematol 2007;137:337)



Recurrent genetic abnormalities

AML with t(6;9)(p23;q34): DEK-NUP214


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Included in WHO 2008 classification under AML with recurrent genetic abnormalities
● First identified by Rowley and Potter in 1976
● 0.7-1.8% of AML
● Occurs in both children and adults (2-66 years old), both sexes equally; median age children 13 years, adults 35 years
● Associated with multilineage dysplasia and basophilia (>2% in marrow and peripheral blood in 44-62% of cases)
● In adults, median white blood cell count is 12x109/L, lower than other AML
● In children, lower hemoglobin values and higher WBC counts than adults
● Associated with dysplasia and a high frequency of FLT3 gene mutations (Am J Clin Pathol 2004;122:348)

Clinical features
=========================================================================

● Anemia, thrombocytopenia, blasts in peripheral blood
● Often pancytopenia, fatigue, bleeding, DIC and increased incidence of infections

Prognostic features
=========================================================================

● Poor prognosis
● <50% remission after chemotherapy; often dead within 1 year after diagnosis (Leukemia 2006;20:1295)

Treatment
=========================================================================

● Allogeneic hematopoietic stem cell transplantation
● Minimal residual disease: monitor by real time RT-PCR (Leukemia 2005;19:1338)
● Current clinical trials include anti-CD33 and FLT3 inhibitors

Micro description
=========================================================================

● 20%+ blasts; intermediate features between AML with maturation (AML-M2), acute promyelocytic leukemia (APL) and acute myelomonocytic leukemia (AML-M4)
● Often ringed sideroblasts (Am J Clin Pathol 1997;107:430)
● Unilineage or multilineage dysplasia (67%, Arch Pathol Lab Med 2008;132:1835)

Positive stains
=========================================================================

● CD9, CD13, CD15, CD33, CD34 (92%), CD38, CD64 subset, CD117, HLA-DR, TdT (50%)

Molecular description
=========================================================================

● t(6;9)(p23;q34) is often sole clonal abnormality; some have complex karyotype
● t(6;9) produces chimeric fusion gene between DEK (6p23) and NUP214 (9q34; formerly known as CAN, Atlas of Genetics and Cytogenetics)
● DEK-NUP214 fusion gene encodes a messenger RNA involved in leukemogenesis
● Also FLT3-ITD (69% pediatric and 78% adult cases), often additional chromosomal abnormalities; FLT3-TDK uncommon
● Patients with FLT3-ITD have higher WBC, higher bone marrow blasts and lower rates of complete remission

Molecular images
=========================================================================


   
Karyotype


Karyotype - bottom row



AML with recurrent genetic abnormalities

AML with t(8;21)(q22;q22) - RUNX1-RUNX1T1


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 30 December 2011, last major update December 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
=========================================================================

● Translocation produces fusion product of RUNX1T1 (ETO) gene on #8q22 and RUNX1 gene on #21q22
● ~ 5% of AML, and 10% of cases of AML-M2 (AML with maturation) in FAB classification
● Most common type of childhood AML
● RUNX1-RUNX1T1 may facilitate accumulation of genetic alterations by suppressing endogenous DNA repair (Blood 2008;111:2190)
● Additional mutations are required for leukemogenesis (Proc Natl Acad Sci USA 2000;97:7521)
● Frequently associated with additional chromosomal translocations which may influence prognosis (Zhonghua Nei Ke Za Zhi 2006;45:918)
● Classify as AML even if initial blast count is < 20%
● RT-PCR and cytogenetics for detection both have limitations (J Clin Oncol 2001;19:2482)
Variant t(8;21): similar clinical features, morphology and immunostaining as classic t(8;21) cases (Am J Clin Pathol 2006;125:267)

Prognostic features
=========================================================================

● Favorable prognosis in adults, although KIT activating mutations confer poorer prognosis
● Good response to chemotherapy and high complete remission rate
● Expression of CD56 and KIT mutations are considered adverse prognostic factors

Case reports
=========================================================================

● With occult mastocytosis (J Clin Pathol 2004;57:324)

Micro description
=========================================================================

● Resembles AML-M2 (AML with maturation) - large blasts, abundant basophilic cytoplasm, frequent large Auer rods and chunky cytoplasmic granules, perinuclear hofs, neutrophil dysplasia
● Trilineage dysplasia present in therapy related cases (Am J Clin Pathol 2002;117:306)
● Peripheral blood contains smaller blasts

Micro images
=========================================================================


Bone marrow smear (Wright-Giemsa):

Myelocytes have abundant cytoplasm with prominent granulation, one myeloblast (slightly left and below center) has prominent Auer rod


Myeloblasts with Auer rods, promyelocytes and other mature cells


Large blast cells with abundant basophilic cytoplasm, often numerous azurophilic granules, may have large granules (pseudo Chediak-Higashi granules), often Auer rods, accompanied by promyelocytes, myelocytes and mature granulocytes with variable dysplasia


H&E and stains

Positive stains
=========================================================================

● CD19 (75-93%) and CD56 in fraction of cases (and may have adverse prognostic significance), aberrant expression compared to classic AML M2 (Am J Clin Pathol 2007;128:550)
● Also PAX5/BSAP (usually weak), OCT2 (75%, Am J Clin Pathol 2006;126:235)
● High levels of CD34 and myeloperoxidase and low levels of CD33 by flow cytometry (Mod Pathol 2004;17:1211)

Negative stains
=========================================================================

● CD20, CD22, CD79a

Molecular / cytogenetics description
=========================================================================

● t(8;21)(q22;q22), RUNX1-RUNX1T1 AML1 gene also called RUNX1, encodes core binding factor alpha

Molecular / cytogenetics images
=========================================================================


t(8;21) with abnormal chromosomes on right, and breakpoints at arrowheads

Various images

Variants



Recurrent genetic abnormalities

Acute myeloid leukemia with t(9;11)(p22;q23); MLLT3-MLL


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 7 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● MLL gene at 11q23 (HRX) encodes a DNA-binding protein that positively regulates expression of target genes, including multiple HOX genes, by methylation of histone H3 lys4 / chromatin remodeling (OMIM 159555, Atlas of Genetics and Cytogenetics)
● 9p22 is MLLT3 / AF9 gene
● Included in WHO 2008 as AML with recurrent cytogenetics
● 3-5% of AML (Anticancer Res 2005;25(3B):1931)
● 9-12% of childhood AML; 2% of adult AML
● Overlaps other categories, including high percentage of topo II inhibitor, therapy related AML (Blood 2003;102:2395); also ALL and biphenotypic leukemia

Clinical features
=========================================================================

● Symptoms: DIC, extramedullary myeloid sarcoma and tissue infiltration (gingiva, skin)
● Translocations occur in AML (intermediate prognosis) and ALL (poor prognosis, Blood Cells Mol Dis 2008;40:192)
● Prognosis may be superior to other AML with 11q23 translocations
● MLL partial tandem duplication AML: prognosis varies from poor (Br J Haematol 2006;135:438) to similar to other AML (Blood 2007;109:5164); of note, also present in 93% of normal cord blood samples at low levels (Leuk Res 2006;30:1091); associated with normal karyotype or trisomy 11

Case reports
=========================================================================

● 60 year old woman with therapy-related ALL with MLL gene rearrangement following treatment of breast cancer (Korean J Lab Med 2010;30:255)
● MLL insertion with MLL-MLLT3 gene fusion in acute leukemia (Cancer Genet Cytogenet 2008;183:53)

Micro description
=========================================================================

● 20%+ blasts / blast equivalents (monoblasts / monocytes) in peripheral blood or bone marrow, usually myelomonocytic or monocytic (AML M4, M5) and occasionally AML with (M2) or without (M1) maturation
● Monoblasts are large cells with abundant, moderate to intensively basophilic cytoplasm, pseudopods, azurophilic granules, vacuoles; round nuclei, lacy chromatin and one or more prominent nucleoli
● Promonocytes have basophilic cytoplasm with granules and occasional large azurophilic granules, vacuoles; irregular and delicately convoluted nuclei

Positive stains
=========================================================================

● Nonspecific esterase
● CD4 weak, CD33 bright, CD36 / CD64 coexpression, CD45, CD56 and HLA-DR

Negative stains
=========================================================================

● Myeloperoxidase
● Children: CD34 and CD117 negative
● Adults: variable CD14, often negative / dim

Molecular description
=========================================================================

● Involves MLL-mixed lineage or myeloid / lymphoid leukemia gene, present in both AML and ALL; is also called HTRX1, HRX and ALL1
● FISH is more sensitive than conventional cytogenetics in detecting MLL; may also detect 11q22-25 rearrangements that are MLL negative (Am J Clin Pathol 2004;122:298)

Variant MLL translocations in AML:
● > 80 translocations described, most commonly MLLT2(AF4) causing ALL; and MLLT3(AF9) causing AML
● Mixed phenotype acute leukemia has t(v;11q23)
● AML-MRC if t(2;11)(p21;q23) or t(11;16)(q23;p13.3)
● Diagnose as t-AML if history of cytotoxic therapy
● Other common translocations: 6q27 (MLLT4), 10p12 (MLLT10), 19p13.1 (ELL) and 19p13.3 (MLLT1)

Molecular images
=========================================================================


   
Partner genes     Diagram of MLL/ALL1 duplication



Recurrent genetic abnormalities

AML with inv(16)(p13.1;q22) or t(16;16)(p13.1;q22); CBFB-MYH11


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 5-8% of all cases of adult AML
● Associated with more frequent hepatosplenomegaly, lymphadenopathy and granulocytic sarcoma than AML in general
● Longer median survival than other AML (Am J Clin Pathol 2003;119:672); when treated with high dose cytarabine in consolidation phase, complete remission rates are 76%-92%
● If translocation present, consider as AML even if initial blast count is < 20%
● FISH recommended if suggestive cell morphology, but negative cytogenetics (J Mol Diagn 2004;6:271)
● Poor prognostic factors: high initial white blood cell count (for complete response); age > 35 years (for disease free survival, Blood 2003;102:462); older patients with KIT mutation for higher risk of relapse
Peripheral blood: monocytosis, high blast counts

Micro description
=========================================================================

● Usually features of AML M4 (acute myelomonocytic leukemia) plus marrow eosinophilia, with dysplastic eosinophils containing large basophilic staining granules, especially in promyelocyte and myelocyte stages, less evident at later stages of eosinophil maturation (Am J Clin Pathol 2003;120:236)
● Granules are large, purple-violet, may obscure cell morphology
● Few mature abnormal eosinophils show faint staining with naphthol ASD chloroacetate esterase (negative in normal eosinophils); blasts have few Auer rods

Micro images
=========================================================================


Bone marrow smears (Wright-Giemsa):
       
Various images (some images associated with cytogenetic changes)

       
Eosinophil precursors show prominent basophilic staining granules

       
H&E, cytogenetics and FISH   H&E, RT-PCR and FISH


Immature cells with folded monocytoid nuclei mixed
with abnormal eosinophils (arrow), containing large
basophilic granules and more normal eosinophil granules

Virtual slides
=========================================================================



Bone marrow smear-AML with inv(16)

Positive stains
=========================================================================

● Granules are positive for chloroacetate esterase and nonspecific esterase
● High Ki-67, CBFbeta-SMMHC (nuclear stain with microgranular or fine-speckled pattern, Am J Surg Pathol 2006;30:1436)

Molecular description
=========================================================================

● Inversion(16) much more common than t(16;16)(p13;q22), but both cause fusion of CBFβ to MYH11
● Smooth muscle myosin heavy chain gene (SMMHC) produces MYH11 at 16p13.1; core binding factor beta (CBF-β) gene produces CBFβ at 16q22; fusion gene is CBFβ - MYH11 protein (Science 1993;261:1041, Proc Natl Acad Sci USA 1998;95:11863)
● May need FISH and RT-PCR to document the genetic alteration, because the rearrangement is subtle and easily overlooked in metaphase preparation
● Trisomy 22 is fairly specific for inv(16); mutations of KIT are seen in 30% of patients
● Multiple fusion transcripts exist (J Mol Diagn 2004;6:22); fusion transcripts appear to upregulate NF-kappaB signaling pathway (Mod Pathol 2007;20:811)

Molecular images
=========================================================================


           
Two G banded chromosomes,      Diagram
show pericentric inversion at #16,
arrowheads point to breakpoints
on abnormal chromosome




AML not otherwise categorized

Myeloid leukemia associated with Down syndrome


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Myeloid proliferations related to Down syndrome (DS) include transient abnormal myelopoiesis (TAM) and myeloid leukemia associated with Down syndrome; separate categories in WHO 2008
● Includes both myelodysplastic syndrome and overt AML since there is no biological, prognostic or therapeutic difference
● Down syndrome patients have 50x incidence of acute leukemia in first 5 years compared to non-DS patients; 50% of these cases beyond the neonatal period are acute megakayrocytic leukemia

Epidemiology
=========================================================================

● Mostly < 5 years old
● 20-30% of children with prior history of TAM within 1-3 years after TAM

Clinical features
=========================================================================

● Involves peripheral blood, bone marrow, spleen and liver
● Mostly within first three years of life, indolent, < 20% blasts and thrombocytopenia
● Preleukemic phase, comparable to refractory cytopenia of childhood (RCC), generally precedes MDS with excess blasts or overt leukemia

Prognostic features
=========================================================================

● Young children with DS and AML with GATA1 mutation have better response to chemotherapy and better prognosis compared to non-DS with AML (treatment with DS-specific protocols)
● Older children with GATA1 mutation have poorer prognosis than AML in non-DS children

Case reports
=========================================================================

● Stillborn fetus with severe disease (Nat Clin Pract Oncol 2007;4:433)

Micro description
=========================================================================

● Preleukemic phase has refractory cytopenia without significant increase of blasts
● Dyspoiesis, occasional erythroid precursors in peripheral blood
● Erythrocytes: anisopoikilocytosis, dacryocytes
● Thrombocytopenia, giant platelets
● Bone marrow blasts have round to slightly irregular nuclei and moderate amounts of basophilic cytoplasm, blebs may be present

Micro images
=========================================================================


    
Acute myeloid leukemia  Echinocyte


Blasts in transient leukemia associated with Down syndrome

Positive stains
=========================================================================

● CD4, CD7, CD13, CD33, CD34 (50%), CD36, CD41 (70%), CD42, CD56 (70%), CD61, CD71, CD117, TPO-R and IL-3R

Negative stains
=========================================================================

● CD14, CD15, MPO and Glycophorin A

Molecular description
=========================================================================

● Trisomy 21 and acquired mutations in GATA1 gene
● > 5 years old may not have GATA1 mutation
● Trisomy 8 common
● Monosomy 7 very rare



Recurrent genetic abnormalities

AML with FLT3 mutations


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not a WHO diagnosis
● Mutations of FMS-related tyrosine kinase 3 (FLT3, gene located on 13q12) occur in all types of AML and MDS (Atlas of Genetics and Cytogenetics)
● Most frequent molecular abnormality in AML (20-40% of cases)
● AML: mutations occur most often in t(6;9)(p23;q34), APL t(15;17), AML with normal karyotype
● Usually peripheral leukocytosis and normal cytogenetics
CD135 is receptor for FLT3 ligand / FLT3L

Prognostic factors
=========================================================================

● Mutations include internal tandem duplication within juxtamembrane domain (ITD, 75-80%) and tyrosine kinase domain (TKD) in codon 836 (20-35%)
● FLT3-ITD: poor prognosis (Blood 2002;100:1532)
● FLT3-ITD with NPM1, t(15;17), t(8;21), inv(16) and t(16;16): worse prognosis
● FLT3-ITD with CEBPA: unclear prognosis
● FLT3-TKD: doesn’t affect prognosis (Blood 2008;111:2527)

Diagrams
=========================================================================


   
FLT3 structure      Molecular heterogeneity of cytogenetically normal AML

Treatment
=========================================================================

● C220 and midostaurin are in phase II clinical trials for AML patients with FLT3 mutations (Clinical Trials)
● Sorafenib may show significant activity (Blood 2009;113:6567, J Natl Cancer Inst 2008;100:184)

Micro description
=========================================================================

● Monocytic differentiation
● Usually AML M2, M4, M5b (Blood 2008;111:2527)

Molecular description
=========================================================================

● Usually normal cytogenetics
● Most common mutation is internal tandem duplication mutation (ITD)
● Cooperating mutations with NPM1, CEBPA and MLL-PTD

Molecular images
=========================================================================



Activating ITD mutations



Recurrent genetic abnormalities

AML with myelodysplastic related changes


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 19 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 20%+ blasts in peripheral blood or bone marrow AND (a) prior diagnosis of MDS or MDS/MPN; (b) cytogenetic abnormalities associated with MDS or (c) multilineage dysplasia in > 50% of the cells of at least 2 separate bone marrow lineages
● Excludes patients with (a) prior history of cytotoxic therapy or unrelated disease or (b) cytogenetic abnormalities associated with AML with recurrent genetic abnormalities
● Arises either as de novo AML, from existing myelodysplastic syndrome or from myelodysplastic / myeloproliferative neoplasm
● Includes what was previously called refractory anemia with excess blasts in transformation
● Previously called AML with multilineage dysplasia
● Recommended to include reason for diagnosis, blast count or presence of mutations (NPM1, CEBPA, FLT3)
● Examples: (a) AML-MRC (multilineage dysplasia); (b) AML-MRC (previous MDS or MDS/MPN history); (c) AML-MRC (MDS related cytogenetics and presence of FLT3 mutation)

Clinical features
=========================================================================

● Usually presents with severe pancytopenia
● Both children and adults; represent 24-35% of all AML
Children: occurs in 3% with de novo AML, good response to treatment (Int J Hematol 2007;86:358)
Adults: median age 61 years; higher incidence in AML in older individuals

Prognostic features
=========================================================================

● Poorer prognosis than classic AML, particularly if adverse cytogenetics (Eur J Haematol 2002;68:203), and history of MDS or MDS/MPN (Blood 2010;116:2742), but see Blood 2008;111:1855
● Low blast count less clinically aggressive

Micro description
=========================================================================

● Dysplasia in 50%+ of cells of 2 or more lineages
● Often panmyelosis, usually dysplastic megakaryocytes
● Variably cellular marrow with 20%+ blasts
Dysgranulopoiesis: hypogranular neutrophils, hyposegmented (Pelger-Huët cells) and bizarrely segmented (as seen in peripheral blood)
Dyserythropoiesis: megaloblastosis, karyorrhexis, nuclear irregularity, fragmentation, multinucleation, ringed sideroblasts, cytoplasmic vacuoles and PAS+
Dysmegakaryopoiesis: micromegakaryocytes, normal or large megakaryocytes with non-lobulated or multiple nuclei

Micro images
=========================================================================

Various images
Patients with prior MDS

Images contributed by Daniela Mihova, MD:

Positive stains
=========================================================================

● CD34, CD117 and HLA-DR

Molecular description
=========================================================================

● Trisomy 8, abnormalities of #5 or #7 are common
● Also t(3;5)(q25;q34-35) involving MLF1 and NPM (Hum Pathol 2003;34:809)
● Mutations in NPM1, CEBPA, FLT3-ITD, FLT3-D835, N-RAS and MLL-PTD (Blood 2009;113:1906)
● Complex karyotype including 3+ unrelated abnormalities, none of which is included in AML with recurrent genetic abnormalities

● Unbalanced abnormalities: -7/del(7q), -5/del(5q), i(17q)/t(17p), -13/del(13q), del(11q), del(12p)/t(12p), del(9q), idic(X)(q13) (eMedicine)

● Balanced abnormalities:
● t(11;16)(q23;p13.3) - therapy related myeloid neoplasms should be excluded before diagnosis of AML-MRC
● t(3;21)(q26.2;q22.1) - therapy related myeloid neoplasms should be excluded before diagnosis of AML-MRC
● t(1;3)(p36.3;q21.1)
● t(2;11)(p21;q23) - therapy related myeloid neoplasms should be excluded before diagnosis of AML-MRC
● t(5;12)(q33;p12)
● t(5;7)(q33;q11.2)
● t(5;17)(q33;p13)
● t(5;10)(q33;q21)
● t(3;5)(q25;q34) – young patients; involving MLF1 and NPM (Hum Pathol 2003;34:809)

● Common in MDS but not sufficient for diagnosis of AML-MRC by themselves: +8, del(20q), and loss of Y (in older man)

Differential diagnosis
=========================================================================

Acute erythroid leukemia
Acute megakaryoblastic leukemia
AML-M2
AML-M6a
● AML-NOS
● AML with recurrent genetic abnormalities
t-AML



Recurrent genetic abnormalities

Therapy-related myeloid neoplasms


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Included as a separate group in WHO 2008 classification
● May present as t-MDS, t-MDS/MPN or t-AML ("t-" means therapy related)
● May occur post-chemotherapy or post-radiation therapy
● Rarely occurs after therapy for de novo AML (Leuk Res 2008;32:1043)
● Includes two broad categories (see below): (1) alkylating agents or radiotherapy and (2) topoisomerase II inhibitor therapy; both cause direct DNA damage, but with different genetic and clinical features
● Note: t-MDS: has close relationship to t-AML
● t-AML has similar genetic abnormalities as de novo myelodysplasia and AML, but different frequencies (Hematology Am Soc Hematol Educ Program 2007:392)
● Survival varies by cytogenetics (Hematology Am Soc Hematol Educ Program 2007:453, Pediatr Blood Cancer 2008;50:17)
● Risk in children and adults may actually be similar (J Toxicol Environ Health B Crit Rev 2007;10:379)
● Prognosis is poor and similar in both t-MDS and t-AML, regardless of blast count (Haematologica 2007;92:1389)


Due to Alkylating agents

General
=========================================================================

● Alkylating agents: busulfan, carboplatin, carmustine, chlorambucil, cisplatin, cyclophosphamide, dacarbazine, lomustine, melphalan, mitocyn C, nitrogen mustard, procarbazine, thiotepa
● Occurs median 5 years after initiation (range, 2-11 years)
● Risk is associated with patient age and cumulative dose of alkylating agent
● Typically presents with myelodysplastic syndrome and bone marrow failure
● May progress to AML or may die without progression

Prognostic features
=========================================================================

● Poor prognosis (worse than de novo AML with comparable features); median survival is 7-8 months
● Survival < 1 year if abnormalities of #5, #7 or complex changes

Micro description
=========================================================================

● Presents as MDS, AML or MDS/MPN (CMML)
● Hypocellular marrow; severe dysplastic changes in blood and marrow in 60%
● Basophilia, myelofibrosis and ringed sideroblasts common (>15%)
● In MDS phase (50%), < 5% myeloblasts
● Primary neoplasm may persist in conjuction with therapy related myeloid neoplasm

Molecular description
=========================================================================

● Abnormalities of chromosomes 5 or 7 or complex cytogenetic abnormalities


Due to Topoisomerase II inhibitors

General
=========================================================================

● Topoisomerase II inhibitors: actimomycin, amsacrine, doxorubicin, etoposide, mitaxantrine, teniposide
● Abrupt onset <1 to 3 years after initiation of etoposide or teniposide with doxorubicin
● Presents as acute monocytic or myelomonocytic leukemia

Prognostic features
=========================================================================

● Poor prognosis; worse than de novo AML counterpart
● Better if have recurrent genetic abnormalities; better than t-MDS

Molecular description
=========================================================================

● Usually 11q23 and 21q22 abnormalities
● Also t(15;17), inv(16), t(16;16) and (9;11)


Due to other agents

General
=========================================================================

● Non specific immunophenotype: positive for CD7, panmyeloid markers (CD13, CD33), CD34, CD56

Case reports
=========================================================================

● t(4;11) related AML post-rituximab and fludarabine for SLL (Cancer Genet Cytogenet 2007;177:143)

Micro images
=========================================================================



Left: t-AML with t(8;21); right: t-AML with t(16;21)



AML with recurrent genetic abnormalities

Microgranular variant of acute promyelocytic leukemia


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 20 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Formerly called AML-M3v
Note: “variant” APL without further description may mean microgranular variant or an APL variant other than t(15;17)
● Peripheral blood white blood count usually elevated, in contrast to hypergranular form
Diagnosis: cytogenetics recommended because other AML cases may appear similar (Am J Clin Pathol 2002;117:651)

Prognostic factors
=========================================================================

● Treatment with ATRA and anthracyclines recommended for APL
● CD56 expression associated with less favorable prognosis

Case reports
=========================================================================

● 5 year old girl with Down’s syndrome (J Med Case Rep 2007;1:147)
● 69 year old woman post-chemotherapy for breast cancer (Cancer Genet Cytogenet 2002;138:143)
● Nine years after diagnosis of essential thrombocythemia (Am J Hematol 2002;71:114)

Micro description
=========================================================================

● Predominatly bilobed leukemic cells have fewer and smaller cytoplasmic granules, usually multiple Auer rods but less than classic (hypergranular) promyelocytic leukemia
● Nuclei is folded, convoluted and markedly irregular

Micro images
=========================================================================


     
Promyelocytes have abundant fine azurophilic cytoplasm with
variable size and basophilia, markedly lobulated and invaginated nuclei

     
Small hyperbasophilic promyelocytes with prominent cytoplasmic
budding, most cells have sparsely granular cytoplasm and lobulated nuclei

Positive stains
=========================================================================

● Usually CD2 (Leukemia 1995;9:1461), CD13, CD33, CD34 (relatively more common than hypergranular variant, Haematologica 2006;91:311) and myeloperoxidase (strong)

Molecular description
=========================================================================

● Associated with FLT-3-ITD mutations (Br J Haematol 2004;125:463) and different gene expression profiles than hypergranular APL (Genes Chromosomes Cancer 2005;43:113)

Variant translocatios in acute promyelocytic leukemia:
● A subset of cases which morphologically resemble APL and show variant translocation involving the RARA
● Fusion partners include:
     ● ZBTB16 (previously known as PZLF) on 11q23
     ● NUMA1 (nuclear matrix associated gene1) on 11q13
     ● NPM1 (nucleophosmin gene) at 5q35
     ● STAT5B at 17q11.2

Electron microscopy description
=========================================================================

● Stellate array of endoplasmic reticulum is characteristic

Electron microscopy images
=========================================================================



Smaller granules than hypergranular variant, granules are more uniform in size and endoplasmic reticulum is prominent


Small granules and stellate array of endoplasmic reticulum

Differential diagnosis
=========================================================================

Other AML: see Am J Clin Pathol 2002;117:651



Recurrent genetic abnormalities

Acute promyelocytic leukemia (APL) with t(15;17)(q22;q12); PML-RARα


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Either hypergranular (this section) or microgranular / hypogranular
● 5-8% of AML cases
● Formerly called AML M3
● Median age 35-40 years, but can occur at any age
● Decreased WBC count (hypergranular variant) at presentation with abnormal promyelocytes
● Usually disseminated intravascular coagulation (DIC) and hemorrhage before or during induction chemotherapy, which may cause early death
● Rarely organomegaly, extramedullary disease, skin involvement (detect with FISH, Mod Pathol 2005;18:1569)
Criteria for diagnosis: most cells (> 50%) are abnormal promyelocytes with heavy cytoplasmic granulation that may obscure the nuclear cytoplasmic margin, often reniform or bilobed nucleus; cells with multiple Auer bodies usually present; also bundles of Auer rods ("faggot cells" - resembles bundle of sticks)
Note: if t(15;17) present, diagnose as AML even if initial blast count is < 20%

Prognostic factors
=========================================================================

● In children, age < 10 years is favorable (Cancer 2006;106:2495)
Survival: excellent if DIC and hemorrhage are adequately controlled; excellent in adults with complete remission

Case reports
=========================================================================

● 45 year old man with fatigue (Univ Pittsburgh Case #457)

Treatment
=========================================================================

● Combination chemotherapy required for sustained remissions (Hematology Am Soc Hematol Educ Program 2006:147)
● All trans retinoic acid (ATRA) causes neoplastic promyelocytes to rapidly differentiate into bizarre maturing neutrophils, but patients eventually relapse
● Arsenic trioxide (ATO) for ATRA-refractory patients; induces differentiation at low doses, marrow necrosis at high doses (Mod Pathol 2000;13:954)

Micro description
=========================================================================

● Most cells are hypergranular promyelocytes (abundant cytoplasm, round / oval and frequently eccentric nuclei with occasional clefts or indentations, moderately condensed chromatin and indistinct nucleoli) with heavy red / purple cytoplasmic granulation that may obscure nuclear borders
● 90% have multiple Auer rods in some cells, which may resemble bundles of sticks
● Reniform (kidney shaped) nucleus; may have basophilic cytoplasm, < 20% myeloblasts
Post-treatment: may be difficult to differentiate residual disease (promyelocytes not in any particular location) from regenerating marrow (promyelocytes are perivascular and endosteal)

Micro images
=========================================================================


Bone marrow smears (Wright-Giemsa):

Abundant azurophilic granules; left image has 2 microgranular promyelocytes with basophilic cytoplasm and lobulated nuclei


Numerous Auer rods in bundles

Bone marrow biopsy:
              
Bone marrow is almost completely replaced   Promyelocytes are relatively uniform with abundant
by promyelocytes with abundant cytoplasm,  cytoplasm containing dense azurophilic granules and
oval / round nuclei that are often eccentrically multiple Auer rods, nuclei are round, oval and lobulated
located, with occasional indentations/clefts,
somewhat condensed chromatin and
indistinct nucleoli

Treatment related:
              
Post-chemotherapy smear shows cell    Before and after arsenic trioxide
with numerous Auer rods in bundles

Stains:
        
CD99 (figures 3C/3D)        H&E and CD99 (fig A1/A2)

Other sites:

Various images

Positive stains
=========================================================================

● CD9, CD11a and CD11b (post-ATRA: Arch Pathol Lab Med 2003;127:e4 or arsenic trioxide: Mod Pathol 2000;13:954)
● Bright and heterogenous espression (flow cytometry): CD2 (23%), CD13, CD33, CD64 (27%), CD79a (86% but varies by clone, Am J Clin Pathol 2007;128:306), myeloperoxidase (strong) and HLA-DR (9%)
● Variable CD34, CD71 and CD99

Negative stains
=========================================================================

● CD11b (but post-treatment is positive), CD11c (Am J Clin Pathol 1998;109:211), CD14, CD36, CD41, CD61 and glycophorin A

Molecular description
=========================================================================

● t(15;17) translocation not found in other AML subtypes (Atlas of Genetics and Cytogenetics)
● Breakpoints at PML gene on #15q22 and retinoic acid receptor alpha (RARα) gene on #17q21
● Hybrid mRNA produces abnormal retinoic acid receptor that blocks myeloid differentiation
● Cases without Auer rods usually have additional chromosomal abnormalities besides t(15;17) (Am J Clin Pathol 1999;112:113)

Table 3: cytogenetic abnormalities in APL (eMedicine):

Translocation    Genes Involved    All-Trans-Retinoic Acid Response
t(15;17)(q21;q11) PML/RARα      Yes
t(11;17)(q23;q11) PLZF/RARα      No
t(11;17)(q13;q11) NuMA/RARα    Yes
t(5;17)(q31;q11)   NPM/RARα     Yes
t(17;17)     stat5b/RARα    Unknown

Molecular images
=========================================================================


          
t(15;17) - arrowheads at breakpoints  Karyotype
on abnormal chromosomes


FISH - negative and positive control of t(15;17)

Electron microscopy description
=========================================================================

● Auer rods have tubular substructure, markedly dilated endoplasmic reticulum and stellate complexes of rough ER
● Nucleus has dispersed chromatin and prominent nucleolus

Electron microscopy images
=========================================================================


               
Cytoplasm has numerous dense granules and   Cross section of Auer rod shows characteristic tubular structure
several Auer rods, nucleus has dispersed
chromatin and prominent nucleolus



Recurrent genetic abnormalities

Acute promyelocytic leukemia with t(V;17)(V;q12)


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

Note: “variant” APL without further description may mean microgranular (morphologic) variant or cytogenetic variant other than t(15;17)
● Uncommon, involves retinoic acid receptor alpha on #17 but not PML gene on #15
● t(11;17) is most common; also called ZBTB16-RARα variant
● Symptoms: disseminated intravascular coagulation / DIC common (Atlas of Genetics and Cytogenetics-t(11;17))
● May NOT respond to all-trans retinoic acid therapy; may be more aggressive than classic APL (Blood 1995;85:1083)
● Recommended to combine cytogenetics, FISH and molecular biology to document presence / absence of PML-RARα fusion gene in complex cases (Cancer Genet Cytogenet 2005;159:69)

Case reports
=========================================================================

● 23 year old man with tuberculosis (Korean J Hematol 2012;47:229)
● 31 year old woman with t(17;20) masking t(15;17) variant (Cancer Genet Cytogenet 2006;168:73)
● 66 year old man with PRKAR1A gene (Blood 2007;110:4073)

Micro description
=========================================================================

● Features are intermediate between hypergranular acute promyelocytic leukemia (M3) and acute leukemia with maturation (M2) - most cells have many granules and regular nuclei; usually no Auer rods but increased pseudo Pelger-Huet cells

Micro images
=========================================================================



Cells with many granules, regular nuclei, no Auer rods


t(11;17)(q23;q21) variant shows promyelocytes in peripheral blood and marrow

Molecular / cytogenetics description
=========================================================================

● Involves RAR alpha and either PLZF / ZBTB16 (11q23), NUMA (11q13), NPM (5q31) or STAT5b genes (Leukemia 2002;16:1927)

Molecular / cytogenetics images
=========================================================================



t(11;17)(q23;q21) variantw

Differential diagnosis
=========================================================================

● t(11;17) may resemble AML with 11q23 abnormality (Cancer Genet Cytogenet 2005;159:168)



Recurrent genetic abnormalities

Acute promyelocytic leukemia - therapy related


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not a WHO diagnosis
● Prior tumor is usually breast carcinoma, other solid tumor or non-Hodgkin’s lymphoma treated with radiation or chemotherapy (J Clin Oncol 2003;21:2123)
● Usually develops within 3 years, with no preleukemic phase

Pathophysiology
=========================================================================

● Mitoxantrone, etoposide or their metabolites stimulate topoisomerase II to cleave different sites in PML and RARA, which are then translocated (N Engl J Med 2005;352:1529)


Breakpoint Hot Spot in PML Intron 6 in Mitoxantrone-Related APL

Case reports
=========================================================================

● 8 year old girl with secondary APL post chemotherapy for non Hodgkin lymphoma (J Pediatr Hematol Oncol 2004;26:427)
● 47 year old woman with therapy-related APL after radioactive iodine for thyroid cancer (J BUON 2007;12:129)
● 69 year old woman with microgranular APL post-chemotherapy for breast cancer (Cancer Genet Cytogenet 2002;138:143)

Micro description
=========================================================================

● Classic findings of APL plus dyserythropoiesis and dysmegakaryopoiesis

Molecular description
=========================================================================

● t(15;17)(q22;q12), often with additional abnormalities
● PML-RARa in most cases; FLT-3 gene mutations in 42% (Am J Clin Pathol 2005;123:840)



AML not otherwise categorized

Acute myeloid leukemia with minimal differentiation (FAB AML M0)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● No definitive evidence of myeloid differentiation by morphology and light microscopy cytochemistry; need immunohistochemistry, flow cytometry, or EM cytochemistry to characterize as myeloid
Criteria for diagnosis: nongranular blasts; less than 3% of blasts are positive for myeloperoxidase (MPO), Sudan Black B (SBB) or naphthol-ASD-chloroacetate esterase (CAE) by enzyme cytochemistry, although blasts may express myeloperoxidase by EM or immunohistochemistry; blasts do not express classic lymphocyte antigens, but may aberrantly express some lymphocyte antigens

Clinical features
=========================================================================

● 5% or less of AML cases; any age, mostly infants or older adults
● Typically presents with anemia, thrombocytopenia, neutropenia, marrow failure, but may have leukocytosis with markedly increased blasts
● Children (Blood 2007;109:2314) and adults (Br J Haematol 2001;113:737) may have poorer outcome than other AML subtypes
● Enzyme cytochemistry: negative for nonspecific esterase, although may have non-specific weak or focal reaction distinct from monocytic cells

Case reports
=========================================================================

● 58 year old man with minimally differentiated acute myelogenous leukemia (AML-M0) granulocytic sarcoma in oral cavity (Oral Oncol 2002;38:516)
● Subtelomeric t(5;9)(q35.3;q34.3) and deletion of RB1 gene (Cancer Genet Cytogenet 2008;181:36)
● Deletion of (15)(q11.2q22) (Cancer Genet Cytogenet 2008;184:57)

Micro description
=========================================================================

● Medium sized-blasts, round or slightly indented nuclei with dispersed chromatin
● One or two nucleoli, agranular cytoplasm with varying degree of basophilia and no Auer rods
● Rarely small blasts with condensed chromatin and scant cytoplasm that may resemble lymphoblasts
● Occasionally, residual normal population of maturing neutrophils may be present
● Bone marrow: markedly hypercellular with poorly differentiated blasts

Micro images
=========================================================================


Bone marrow smear (Wright-Giemsa):
   
No differentiated features


M0 (figure A) compared to other AML

Bone marrow biopsy:

Complete replacement of marrow by blasts without differentiation

Stains:
         
Blasts are positive for  CD99          Myeloblasts are negative for myeloperoxidase
myeloperoxidase by IHC              by cytochemistry with positive staining in neutrophil

Flow cytometry description
=========================================================================

● Pediatric AML-M0 is usually CD33 bright, TdT-, CD34- and CD13-/weak (Am J Clin Pathol 2000;113:193, Clinical Flow Wiki)

Flow cytometry images
=========================================================================



Various gating plots

Positive stains
=========================================================================

● CD13, CD33 (Am J Clin Pathol 2001;115:876), CD34, CD117 (Am J Clin Pathol 2002;117:380), HLA-DR and CD38
● Variable expression of myeloperoxidase, Sudan Black B, TdT (50%), CD2, CD4, CD7 (40%) and CD16 / CD56

Negative stains
=========================================================================

● CD11b (usually), CD14 (usually), CD15 (usually), CD36 (usually), CD41, CD61, CD64 (usually, Arch Pathol Lab Med 2007;131:748) and most lymphocyte antigens(CD5, cCD3, cCD79a, cCD22)
● Glycophorin A

Molecular description
=========================================================================

● Often complex chromosomal abnormalities; tend to have more -5/del(5q), -7/del(7q), +8 and del(11q), but these should be reclassified as AML-MRC
● AML1 / CBFA / RUNX1 (27%) and strong association with trisomy 13 and FLT3 mutation (16-22%, Haematologica 2007;92:1123)
● More often trisomy 21 and hypodiploidy than other AML, although outcome is similar (Blood 2007;109:2314)

Electron microscopy description
=========================================================================

● Resembles myeloblasts; may show focal myeloperoxidase+ granules

Electron microscopy images
=========================================================================


   
Granules are myeloperoxidase positive

Differential diagnosis
=========================================================================

● Acute leukemia of ambiguous lineage
ALL
● AML-MRC
Mixed phenotypic leukemia
AML-M7 (megakaryoblastic)
● Leukemic phase of large cell lymphoma



AML not otherwise categorized

Acute myeloid leukemia without maturation (FAB AML M1)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 7 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 10-20% of AML cases, 44% in one Brazil hospital (Sao Paulo Med J 2006;124:45)
● Usually adults (median age 46 years), present with anemia, thrombocytopenia and neutropenia; may have leukocytosis with markedly increased blasts
● 4% of childhood AML (Orphanet May 2004)

Clinical features
=========================================================================

Criteria for diagnosis: 90%+ of nonerythroid cells in marrow are myeloblasts; <10% granulocytic elements; 3%+ of blasts must be positive for myeloperoxidase or Sudan Black B and / or Auer rods by enzyme cytochemistry
Enzyme cytochemistry: 3%+ of blasts are positive for myeloperoxidase or Sudan Black B (confirm by immunohistochemistry if only 3-10% positive for MPO by enzyme cytochemistry); chloroacetate esterase positive
● Poor prognosis

Case reports
=========================================================================

● 4 year old child with t(6;9) and basophilia (Ann Biol Clin (Paris) 2003;61:352)
● 44 year old man with large and small blasts (Arch Pathol Lab Med 2004;128:448)
● Presenting with arterial thromboembolism (Leuk Res 2007;31:869)

Micro description
=========================================================================

● Typically markedly hypercellular marrow, but normocellular and hypocellular cases occur
● Very immature cells, usually round with few azurophilic cytoplasmic granules or Auer rods
● Nuclei are round or indented; little maturation beyond myeloblast stage
● Cells may may resemble lymphoblasts and not appear myeloid

Micro images
=========================================================================


Bone marrow smears (Wright-Giemsa):
                           
Blasts show mild size variation, have pale   Blasts show more variation in size and     Myeloblasts have irregular nuclei with folding and
to slightly basophilic agranular cytoplasm   number of nucleoli, four blasts have     invagination, one myeloblast has numerous
and uniform nuclei with fine chromatin   Auer rods                 azurophilic granules
and prominent nucleoli

                           
Myeloblasts have marked size variation,    Some variation in size, two myeloblasts    Myeloblasts are large with abundant eosinophilic
irregular nuclei with condensed chromatin, have more intense basophilic cytoplasm   cytoplasm, 2 cells have prominent Auer rods, 1
no nucleoli, one blast has a thin Auer rod    and coarse nuclear chromatin        has azurophilic granules and 2 erythroblasts


Agranular myeloblasts have variation in size,
cytoplasmic volume and cytoplasmic basophilia

Bone marrow biopsy:
             
Marrow is completely replaced by blasts   Biphasic morphology (large and small blasts)
with variable cytoplasm, round/oval nuclei
with mild irregularities and small/indistinct
nucleoli

Peripheral blood smear:

Case with inv(3)(q21q26) shows large and
smaller blasts and normal appearing platelets

Stains:
                           
Myeloblasts are myeloperoxidase+     Numerous granules are Sudan Black B+   H&E and CD99 (figures B1 & B2)

Flow cytometry description
=========================================================================

Clinical Flow Wiki

Positive stains
=========================================================================

● Have 1+ myeloid-associated antigens (CD13, CD33, CD117)
● CD34, CD99 and HLA-DR (70%, Mod Pathol 2000;13:452)
● CD7 (30%); CD2, CD4, CD19 and CD56 in 10-20% of cases; rarely CD11b
● Variable CD15, CD71 and HLA-DR

Negative stains
=========================================================================

● cCD3, CD14 (usually), CD15, cCD22, CD36 (usually), CD41, CD61, CD64 (usually, Arch Pathol Lab Med 2007;131:748), CD65, cCD79a and glycophorin A

Molecular description
=========================================================================

● Associated with t(8;21)
● FLT3 ITD in 22% (Ai Zheng 2007;26:58)
● FLT3 mutations associated with HLA-DR negative patients (Leuk Res 2007;31:921)

Electron microscopy description
=========================================================================

● May have heterogeneous features (Ultrastruct Pathol 1995;19:9)

Electron microscopy images
=========================================================================



Numerous electron dense granules in Golgi region,
also granules throughout cytoplasm and prominent nucleolus

Differential diagnosis
=========================================================================

ALL
AML-M0
AML-M2



AML not otherwise categorized

Acute myeloid leukemia with maturation (FAB AML M2)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 7 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 10% of AML cases; 5% of childhood leukemias (Orphanet May 2004))
● Any age, 20% are < 25 years and 40% are 60 years+
● Anemia, thrombocytopenia, neutropenia; variable number of blasts in peripheral blood
● Variable prognosis
Criteria for diagnosis: 20%+ nonerythroid cells in peripheral blood or bone marrow are myeloblasts; monocytic precursors are < 20% in bone marrow and granulocytes are 10%+ of cells
Enzyme cytochemistry: most blasts are positive for myeloperoxidase or Sudan Black B, and chloroacetate esterase

Case reports
=========================================================================

● 7 year old boy with myeloid sarcoma with acute myeloblastic leukemia (J Coll Physicians Surg Pak 2011;21:369)
● 30 year old man with t(5;11) (Cancer Genet Cytogenet 2007;172:154)
● 35 year old pregnant woman (Rinsho Ketsueki 2011;52:18)
● Three patients with variant t(8;21) (Cancer Genet Cytogenet 2010;199:31)

Micro description
=========================================================================

● Usually hypercellular marrow
● Full range of myeloid maturation through maturing neutrophils, often with abnormal segmentation and 10%+ bone marrow cells with variable degree of dysplasia
● Auer rods in 70% of blasts; myeloblasts with or without azurophilic granules
● Erythroid and megakaryocyte precursors may have dysplastic changes
● Often increased eosinophilic precursors without cytological and cytochemical abnormalities of inv(16)(p13.1q22)
● Basophils may be increased, rarely mast cell hyperplasia (Indian J Pathol Microbiol 2007;50:655)

Micro images
=========================================================================


Bone marrow smears (Wright-Giemsa):
               
Type III myeloblasts (> 20 azurophilic granules) Several myeloblasts, promyelocytes, myelocytes
                        and neutrophils and also several erythroblasts

               
Several myeloblasts and maturing forms,    Large myeloblasts have pseudopods, usually abundant
also neutrophils with agranular cytoplasm     cytoplasm and some with prominent Auer rods


Several blasts have prominent nucleoli and
Auer rods, also a promyelocyte and myelocyte

Stains:
               
Myeloperoxidase+ blasts,            Myeloperoxidase+ blasts and immature
neutrophils are intensely positive         neutrophils, erythroid cells are negative

Bone marrow biopsy:

Markedly hypercellular marrow has predominantly blasts,
also scattered erythroid precursors and eosinophils

Diagnosed as AML with maturation because no t(15;17) and no DIC, but FISH not done, so may actually be acute promyelocytic leukemia:
                   
With specific granules resembling  With numerous promonocytes   Abundant coarse azurophilic granules
Chediak-Higashi anomaly

Flow cytometry description
=========================================================================

Clinical Flow Wiki

Positive stains
=========================================================================

● CD7 (20-30%), CD11b, CD13, CD15, CD33, often CD34, HLA-DR, CD65, CD71 (variable), CD99 and CD117
● Uncommon CD2, CD4, CD19 and CD56 (~10%)

Negative stains
=========================================================================

● CD14 (usually), CD36 (usually), CD41, CD61, CD64 (usually) and glycophorin A

Molecular description
=========================================================================

● t(8;21) cases classified as AML with t(8;21); RUNX1-RUNX1T1; may be only genetic abnormality or part of more complex abnormalities (Cytometry B Clin Cytom 2008;74:25)
● FLT3 mutations associated with HLA-DR negative patients (Leuk Res 2007;31:921)

Electron microscopy images
=========================================================================



Numerous primary granules and fusion of Auer rods

Differential diagnosis
=========================================================================

AML-M1
AML-M3
AML-M4
AML with multilineage dysplasia
AML with t(8;21)
● Leukemoid reaction
Refractory anemia with excess blasts



Recurrent genetic abnormalities

Acute promyelocytic leukemia (APL) with t(15;17)(q22;q12); PML-RARα


Reviewer: Syed Zaidi, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Either hypergranular (this section) or microgranular / hypogranular
● 5-8% of AML cases
● Formerly called AML M3
● Median age 35-40 years, but can occur at any age
● Decreased WBC count (hypergranular variant) at presentation with abnormal promyelocytes
● Usually disseminated intravascular coagulation (DIC) and hemorrhage before or during induction chemotherapy, which may cause early death
● Rarely organomegaly, extramedullary disease, skin involvement (detect with FISH, Mod Pathol 2005;18:1569)
Criteria for diagnosis: most cells (> 50%) are abnormal promyelocytes with heavy cytoplasmic granulation that may obscure the nuclear cytoplasmic margin, often reniform or bilobed nucleus; cells with multiple Auer bodies usually present; also bundles of Auer rods ("faggot cells" - resembles bundle of sticks)
Note: if t(15;17) present, diagnose as AML even if initial blast count is < 20%

Prognostic factors
=========================================================================

● In children, age < 10 years is favorable (Cancer 2006;106:2495)
Survival: excellent if DIC and hemorrhage are adequately controlled; excellent in adults with complete remission

Case reports
=========================================================================

● 45 year old man with fatigue (Univ Pittsburgh Case #457)

Treatment
=========================================================================

● Combination chemotherapy required for sustained remissions (Hematology Am Soc Hematol Educ Program 2006:147)
● All trans retinoic acid (ATRA) causes neoplastic promyelocytes to rapidly differentiate into bizarre maturing neutrophils, but patients eventually relapse
● Arsenic trioxide (ATO) for ATRA-refractory patients; induces differentiation at low doses, marrow necrosis at high doses (Mod Pathol 2000;13:954)

Micro description
=========================================================================

● Most cells are hypergranular promyelocytes (abundant cytoplasm, round / oval and frequently eccentric nuclei with occasional clefts or indentations, moderately condensed chromatin and indistinct nucleoli) with heavy red / purple cytoplasmic granulation that may obscure nuclear borders
● 90% have multiple Auer rods in some cells, which may resemble bundles of sticks
● Reniform (kidney shaped) nucleus; may have basophilic cytoplasm, < 20% myeloblasts
Post-treatment: may be difficult to differentiate residual disease (promyelocytes not in any particular location) from regenerating marrow (promyelocytes are perivascular and endosteal)

Micro images
=========================================================================


Bone marrow smears (Wright-Giemsa):

Abundant azurophilic granules; left image has 2 microgranular promyelocytes with basophilic cytoplasm and lobulated nuclei


Numerous Auer rods in bundles

Bone marrow biopsy:
              
Bone marrow is almost completely replaced   Promyelocytes are relatively uniform with abundant
by promyelocytes with abundant cytoplasm,  cytoplasm containing dense azurophilic granules and
oval / round nuclei that are often eccentrically multiple Auer rods, nuclei are round, oval and lobulated
located, with occasional indentations/clefts,
somewhat condensed chromatin and
indistinct nucleoli

Treatment related:
              
Post-chemotherapy smear shows cell    Before and after arsenic trioxide
with numerous Auer rods in bundles

Stains:
        
CD99 (figures 3C/3D)        H&E and CD99 (fig A1/A2)

Other sites:

Various images

Positive stains
=========================================================================

● CD9, CD11a and CD11b (post-ATRA: Arch Pathol Lab Med 2003;127:e4 or arsenic trioxide: Mod Pathol 2000;13:954)
● Bright and heterogenous espression (flow cytometry): CD2 (23%), CD13, CD33, CD64 (27%), CD79a (86% but varies by clone, Am J Clin Pathol 2007;128:306), myeloperoxidase (strong) and HLA-DR (9%)
● Variable CD34, CD71 and CD99

Negative stains
=========================================================================

● CD11b (but post-treatment is positive), CD11c (Am J Clin Pathol 1998;109:211), CD14, CD36, CD41, CD61 and glycophorin A

Molecular description
=========================================================================

● t(15;17) translocation not found in other AML subtypes (Atlas of Genetics and Cytogenetics)
● Breakpoints at PML gene on #15q22 and retinoic acid receptor alpha (RARα) gene on #17q21
● Hybrid mRNA produces abnormal retinoic acid receptor that blocks myeloid differentiation
● Cases without Auer rods usually have additional chromosomal abnormalities besides t(15;17) (Am J Clin Pathol 1999;112:113)

Table 3: cytogenetic abnormalities in APL (eMedicine):

Translocation    Genes Involved    All-Trans-Retinoic Acid Response
t(15;17)(q21;q11) PML/RARα      Yes
t(11;17)(q23;q11) PLZF/RARα      No
t(11;17)(q13;q11) NuMA/RARα    Yes
t(5;17)(q31;q11)   NPM/RARα     Yes
t(17;17)     stat5b/RARα    Unknown

Molecular images
=========================================================================


          
t(15;17) - arrowheads at breakpoints  Karyotype
on abnormal chromosomes


FISH - negative and positive control of t(15;17)

Electron microscopy description
=========================================================================

● Auer rods have tubular substructure, markedly dilated endoplasmic reticulum and stellate complexes of rough ER
● Nucleus has dispersed chromatin and prominent nucleolus

Electron microscopy images
=========================================================================


               
Cytoplasm has numerous dense granules and   Cross section of Auer rod shows characteristic tubular structure
several Auer rods, nucleus has dispersed
chromatin and prominent nucleolus



AML not otherwise categorized

Acute myelomonocytic leukemia (FAB AML M4)


Reviewer: Daniela Mihova, M.D (see Reviewers page)
Revised: 7 November 2014, last major update September 2012
Copyright: (c) 2001-2014, PathologyOutlines.com, Inc.

General
=========================================================================

Criteria for diagnosis: myeloblasts, monoblasts and promonocytes are 20% or more of nonerythroid cells; myeloblasts and granulocytes are 80% or less of non-erythroid cells; monocyte lineage cells are 20% or more of nonerythroid bone marrow cells
● If less than 20% of bone marrow cells are monocyte lineage, still M4 if blood monocyte count is 5x109/L or higher
Additional criteria (if cannot distinguish early monocytes and early granulocytes): nonspecific esterase reactivity in 20% or more cells or serum lysozyme of 3 times normal
● See also AML with inv(16)(p13;q22) or t(16;16)(p13;q22)

Clinical features
=========================================================================

● 5-10% of AML cases, 3% of childhood leukemia (Orphanet May 2004)
● Children and adults; more common in adults; median age 50 years; male:female is 1.4:1
● Often markedly elevated WBC with anemia and thrombocytopenia, fever, fatigue, variable blasts and promonocytes in peripheral blood; organomegaly, lymphadenopathy and other tissue infiltration (monocytes infiltrate)
● May occur post-therapy (Sichuan Da Xue Xue Bao Yi Xue Ban 2007;38:347)
Enzyme cytochemistry: monoblasts, promonocytes and monoctes are positive for nonspecific esterase; if negative, confirm monocyte lineage with immunophenotyping or EM; at least 3% of blasts are MPO+; double staining for NSE and CAE or MPO may show dual positive cells

Case reports
=========================================================================

● 15 year old girl with catastrophic antiphospholipid antibody syndrome (J Pediatr Hematol Oncol 2004;26:327)
● 21 year old man with AML mimicking primary testicular neoplasm (Eur J Haematol 2003;70:242)
● 23 year old pregnant woman with CD15, CD33 and HLA-DR+ antibodies (The Internet Journal of Hematology 2003;1:1)
● 27 year old man with leukemic ascites (Arch Pathol Lab Med 2005;129:262)
● 30 year old woman with gingival hyperplasia (Univ Pittsburgh, Case 344)

Micro description
=========================================================================

● Myelocytic and monocytic differentiation evident
● Myeloid cells resemble M2 (60% of myeloblasts have Auer rods), but at least 20% of nonerythroid cells are of monocytic lineage
● Monoblasts are large cells with abundant cytoplasm, moderately to intensely basophilic, may have pseudopod formation, scattered fine azuophilic granules and vacuoles
● Round nuclei with lacy chromatin and one or more large nucleoli
● Promonocytes have abundant, less basophilic cytoplasm, which is more obviously granulated with occasional large azurophilic granules and vacuoles, is more irregular, and has delicately folded nuclei

Micro images
=========================================================================


Peripheral smear:

Myeloblast (upper left) with two long slender Auer rods, neutrophilic myelocyte (below myeloblast) with smudged nonspecific granules and promonocyte (right) with abundant azurophilic granules and nucleus with delicate folds and creases

Bone marrow smears (Wright-Giemsa):
             
Mixture of monocytes and neutrophils at  Promonocytes on left have basophilic cytoplasm with
different stages of maturation, also several coarse azurophilic granules; those in upper right have
promonocytes with abundant cytoplasm   abundant pale cytoplasm with delicate nuclear folds
containing fine azurophilic granules and
delicately folded nuclei

             
Three promonocytes have abundant    Five promonocytes and two myelocytes (center),
cytoplasm with fine azurophilic granules,   one containing numerous azurophilic granules and an Auer rod
also dysplastic neutrophil with pseudo-
Pelger-Huet nucleus in upper left

Bone marrow biopsy:
             
Resembling sarcomatoid carcinoma    Markedly hypercellular marrow with heterogeneous cells,
                     including immature monocytes (irregular nuclei and prominent nucleoli) and neutrophils

Other sites:

Leukemic ascites

Stains:
           
Non-specific esterase  CD68         Lysozyme        Peroxidase (myeloid marker)


Chloroacetate esterase stains neutrophils blue,
and nonspecific esterase stains monocytes red-brown

Flow cytometry description
=========================================================================

Clinical Flow Wiki

Positive stains
=========================================================================

● May vary between monocyte and myeloid populations
● CD4, CD11b, CD11c, CD13, CD14 (possibly), CD15, CD33, CD36, CD64, CD65, CD68, CD71 (variable), CD163, HLA-DR, lysozyme and myeloperoxidase
● Variable CD56, CD34 and CD117 (Am J Clin Pathol 2004;122:865)

Negative stains
=========================================================================

● CD41, CD61, glycophorin A and keratin

Molecular description
=========================================================================

● Non-specific cytogenetic abnormalities, +8 in most cases
● Classify as AML with recurrent genetic abnormalities if inv(16)(p13;1q22), t(16;16)(p13.1q22) or t(9;11)(p22;q23) present

Differential diagnosis
=========================================================================

AML M2
● AML with recurrent genetic abnormalities
● CMML
● G-CSF related transient atypical monocytosis (Clin Lab Haematol 2004;26:359)
● Leukemoid reaction
M5
Microgranular M3
t-AML (therapy related)
Myelodysplastic syndrome
● Sarcomatoid carcinoma



AML not otherwise categorized

Acute monoblastic and acute monocytic leukemia (AML- M5)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 10% of AML cases
● High incidence of bleeding disorders (including DIC), organomegaly, lymphadenopathy, gingival hyperplasia, CNS and other tissue involvement (monocytes infiltrate)
● May present with acute respiratory failure (Am J Respir Crit Care Med 2003;167:1329)
● M5a versus M5b: analysis of features is controversial; (a) similar features (Leuk Res 2008;32:269); (b) different expression of CD68 and CD11c (Zhongguo Shi Yan Xue Ye Xue Za Zhi 2006;14:1079); (c) different features (Zhongguo Shi Yan Xue Ye Xue Za Zhi 2006;14:654)
● Similar prognosis as other subtypes (J Clin Oncol 2004;22:1276)

Criteria for diagnosis
=========================================================================

● 80% or more nonerythroid bone marrow cells are monocyte lineage (monoblasts, promonocytes and monocytes)
● A minor neutrophil component < 20%

Micro images
=========================================================================


Erythrophagocytosis in AML M4/M5 (see cell in upper right)

Enzyme cytochemistry
=========================================================================

● Monoblast granules and monocytes are strongly positive for nonspecific esterase and lysozyme, but negative for myeloperoxidase
● More mature monocyte lineage cells may be weakly myeloperoxidase positive
Note: if NSE negative, confirm monocyte lineage with immunostains

Positive stains
=========================================================================

At least two monocytic markers: CD4, CD14, CD11b (80-90%, Am J Clin Pathol 1997;107:283), CD11c (50%), CD36, CD64 (Am J Clin Pathol 1998;110:797), CD68 and HLA-DR
Myeloid markers: CD13 (often very bright), CD33 (often very bright), CD15 and CD65
● CD34 (30%), CD117 and MPO (more often M5b and less often M5a)
Abberant expression: CD7, CD56 (25-40%)
● Lysozyme, CD68 and CD163

Molecular description
=========================================================================

● 11q23 translocations in 19%, trisomy 8 in 17%


Acute monoblastic leukemia (M5a)

General
=========================================================================

● 5-8% of AML
● Children and young adults

Criteria for diagnosis
=========================================================================

● 80%+ of monocyte lineage cells are monoblasts

Case reports
=========================================================================

● 66 year old man with erythropoietin-dependent transformation of refractory anemia with ringed sideroblasts into acute monoblastic leukemia (Blood 2001;98:3492)
● 73 year old woman with coexisting mantle cell lymphoma (Leuk Lymphoma 2005;46:1813)
● 82 year old man with acute monoblastic leukemia following granular lymphocyte proliferative disorder (Rinsho Ketsueki 2011;52:1870)

Micro description
=========================================================================

● Hypercellular marrow with large number of monoblasts
● Monoblasts are large with moderately abundant intensely basophilic cytoplasm, variably basophilic and delicate azurophilic granules but no/rare Auer rods
● May have pseudopods or vacuoles
● Have round nuclei and lacy chromatin with one or more prominent nucleoli but no folds
● Promonocytes have abundant less basophilic cytoplasm with obvious azurophilic granules and nuclei have delicate folds

Micro images
=========================================================================


Blood smear (Wright-Giemsa):

Two monoblasts (left) have abundant cytoplasm with numerous azurophilic granules, promonocyte (right) has abundant cytoplasm with fine azurophilic granules, nuclei have delicate folds

Bone marrow smear (Wright Giemsa):

Monoblasts are large with abundant cytoplasm containing numerous fine azurophilic granules, nuclei lack folds but have slightly coarse chromatin and 2-3 distinct nucleoli

Some monoblasts also show pseudopods

Monoblasts have variable cytoplasm with mild to intense basophilia, some vacuoles but no granules

Monoblasts are larger cells with abundant cytoplasm and round nuclei, and promonocytes are two cells with folded and creased nuclei next to monoblast in center

Bone marrow and skin

Bone marrow biopsy:

Marrow completely replaced by monoblasts-large cells with abundant cytoplasm, round/oval nuclei with prominent nucleoli

Monoblasts are large with abundant pale cytoplasm, numerous vacuoles and prominent pseudopods, nucleoli are distinct

Monoblasts are large with abundant cytoplasm, some nuclei are irregular, many blasts have single prominent nucleoli

Stains:

Monoblasts are intensely positive for nonspecific esterase

Case also has neoplastic plasma cells

Monoblasts are positive for CD68 #1 (KP-1)

Buffy coat smear-vacuoles are PAS+

Positive stains
=========================================================================

● CD13, CD14 (most), CD68, PAS (vacuoles), nonspecific esterase (strong) and lysozyme

Negative stains
=========================================================================

● Myeloperoxidase

Molecular description
=========================================================================

● 75% have cytogenetics abnormalities, including 11q23 in 30% (these cases should be classified as a recurrent genetic abnormality)
● FLT3 mutations in 7%

Electron microscopy images
=========================================================================


Monoblast stained for nonspecific esterase shows scattered electron-dense deposits indicating enzyme activity

Cytoplasm contains focal area of glycogen deposition, also scattered dense granules and a paranuclear fibrillar array

Differential diagnosis
=========================================================================

ALL-L2
AML-M0
AML-M1
AML-M7
AML-MRC
t-AML
Extramedullary myeloid sarcoma


Acute monocytic leukemia (M5b)

General
=========================================================================

● 3-6% of AML
● Affects all ages
● Mature monocytes or promonocytes predominate in peripheral blood (< 80% of monocyte lineage cells are monoblasts, usually < 20%)
● Treatment may cause tumor lysis syndrome, DIC and falsely elevated platelet counts (Arch Pathol Lab Med 1999;123:1111)

Case reports
=========================================================================

● 47 year old man with spontaneous remission after infection (Int J Lab Hematol 2007;29:386)
● 50 year old man with cutaneous disease, (Arch Pathol Lab Med 2005;129:425)
● 63 year old man with preceding aleukemic leukemia cutis (Case Rep Oncol 2011;4:547)
● 74 year old man with mycosis fungoides now with increased circulating immature mononuclear cells (Univ Pittsburgh case #460)
● 77 year old man with coexisting myeloma (Arch Pathol Lab Med 2003;127:1506)
● With mononucleosis syndrome due to varicella zoster virus (Eur J Haematol 2002;68:236)

Micro description
=========================================================================

● Leukemic cells are often promonocytes with less basophilic cytoplasm and more azurophilic granules than monoblasts
● Have folded or cerebriform nuclei with fine chromatin
● Erythrophagocytosis is common

Micro images
=========================================================================


Blood smears (Wright-Giemsa):

Promonocytes have abundant cytoplasm with azurophilic granules that are myeloperoxidase negative, nuclei have delicate folds, nucleoli are inconspicuous

Bone marrow smears (Wright-Giemsa):

Monocytic cells have range of differentiation, promonocytes have nuclei with delicate folds

Two myeloblasts (round/oval nuclei, high N/C ratio) and three promonocytes (abundant cytoplasm with delicate azurophilic granules, lobulated nuclei with delicate folds)

Bone marrow biopsy:

Cells have moderate granular cytoplasm, nuclei are lobulated and indented with indistinct nucleoli

Treatment:

Before and after treatment, alpha naphthyl butyrate esterase

Stains:

Monocytes and one neutrophil are intensely positive for nonspecific esterase

Skin lesions: H&E and nonspecific (alpha naphthyl butyrate) esterase

Electron microscopy images
=========================================================================


Promonocyte has cytoplasm with numerous small cisternae of rough endoplasmic reticulum and a few scattered dense granules, nucleus is markedly lobulated with marginated chromatin

Positive stains
=========================================================================

● CD13, CD14 (most), CD68, CD61 (some)

Negative stains
=========================================================================

● CD41, glycophorin A

Flow cytometry description
=========================================================================

AMoL (Acute Monoblastic/Monocytic Leukemia) (M5)

Molecular description
=========================================================================

● 30% have cytogenetics abnormalities, including 11q23 in 12% (these cases should be classified as a recurrent genetic abnormality)
● FLT3 mutations in 30%
● t(8;16)(p11;p13) fuses MOZ gene at 8p11 with CBP gene at 16p13 and is associated with erythrophagocytosis and coagulopathy

Differential diagnosis
=========================================================================

AML M4
● Malignant histiocytic disorders
Microgranular acute promyelocytic leukemia
Myelodysplastic syndrome: to distinguish, count promonoblasts in M5 with monoblasts



AML not otherwise categorized

Acute erythroid leukemia (AML-M6)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Includes two subtypes: erythrod / myeloid leukemia (M6a, more common) or pure erythroid leukemia (M6b, rare) (eMedicine)
● One letter suggests that most cases may now be defined as AML with multilineage dysplasia (Haematologica 2004;89:ELT11)


Erythroleukemia (M6a)

General
=========================================================================

● 1% of AML cases
● Children to >age 90, usually adults, male predominance
● 20% of therapy related AML but only 1% of de novo AML
● Much more common than pure erythroid leukemia (Haematologica 2002;87:148)
● Di Guglielmo syndrome: nonspecific clinical findings of anemia, thrombocytopenia, variable neutropenia
● Hemophagocytic lymphohistiocytosis: recurrent and specific complication (Br J Haematol 2011;153:669, Br J Haematol 2011;153:669)
● Rare extramedullary involvement
● Peripheral smear may have prominent erythroblasts

Diagnosis
=========================================================================

● 50%+ of nucleated marrow cells are erythroid lineage, including erythroblasts, 20%+ of nonerythroid cells are myeloblasts (Leuk Lymphoma 2006;47:683)
● Dyserythropoiesis is prominent
● Dysplasia in <50% of cells in only 1 cell lineage
● No MDS/MPN, no erythropoietin, cytotoxic or radiation therapy, no AML or MDS cytogenetic abnormalities, no Ph chromosome or t(9;22)
● May be familial (Br J Haematol 1987;65:313)

Prognostic factors
=========================================================================

● Poor prognosis but better than pure erythroid leukemia (pEL, M6b), better overall survival if non-complex cytogenetic abnormalities
● Treated with bone marrow transplantation

Case reports
=========================================================================

● Congenital erythroleukemia presenting as infantile hemangioma (Plast Reconstr Surg 2007;119:70e)
● 43 year old woman with leukocytosis, congenital disease presenting as liver failure (Arch Pathol Lab Med 2003;127:1362)
● Associated with low dose methotrexate for rheumatoid arthritis (Clin Exp Rheumatol 1999;17:S95)
● KIT(D816V+) systemic mastocytosis associated with KIT(D816V+) acute erythroid leukaemia (J Clin Pathol 2009;62:1147)
● Erythroleukemic infiltration of lymph node (Hum Pathol 1984;15:1090)

Micro description
=========================================================================

● Hypercellular marrow
● Predominance of erythroid precursors with PAS+ cytoplasmic vacuoles (evidence of dysplasia)
● Abnormal nuclear development including megaloblastoid cells, karyorrhexis and gigantoblasts with multiple nuclei
● Often dysplastic platelets and megakaryocytes with megaloblastoid nuclei
● 20%+ nonerythroid cells are myeloblasts, and may have Auer rods
● May have ringed sideroblasts

Micro images
=========================================================================


Bone marrow smear (Wright-Giemsa):

Numerous myeloblasts and erythroid precursors at all stages of maturation

Megaloblastoid erythroblast and three myeloblasts

Multinucleated erythroblast has megaloblastoid chromatin

Acute erythroleukemia


20%+ each of pronormoblasts and myeloblasts (formerly M6c)

Bone marrow biopsy:

Early to late stage erythroblasts, small megakaryocytes at upper and lower margins, marked reduction in granulocytes

Marrow is replaced by blasts with variable size and few mature erythroid forms, immature erythroid cells have dispersed chromatin and prominent nucleoli

Blood smear:

20:1 ratio of erythroid precursors to WBC in asplenic patient with erythroleukemia, most precursors are at polychromatic and basophilic maturation stages

Stains:

Immature erythroid cells are hemoglobin A+

Positive stains
=========================================================================

Erythroid cells: glycophorin A (mature forms), hemoglobin A, CD36, CD71, CD117(dim), PAS (vacuoles), variable MRD-1 and P-glycoprotein (Mod Pathol 2000;13:407)
Myeloid cells : Myeloperoxidase, CD13, CD33, CD36, CD71, CD117, HLA-DR

Negative stains
=========================================================================

Erythroid cells: myeloperoxidase, CD13, CD33, CD34 (or weak), HLA-DR (or weak), CD41 and CD61
● Immature erythroblasts may be negative for hemoglobin A or glycophorin A
Leukemic blasts: loss of inhibin (Arch Pathol Lab Med 2001;125:198)

Flow cytometry description
=========================================================================

Acute Erythroblastic leukemia (M6)

Differential diagnosis
=========================================================================

● AML-M0
● AML with multilineage dysplasia
● B/T ALL
● Burkitt lymphoma
● Congenital dyserythropoiesis
● Megakaryoblastic leukemia (AML M7)
● Megaloblastic anemia
● Myeloproflierative neoplasm with erythroblasts
● Parvovirus infection
● Plasma cell myeloma
● RAEB-2, t-AML and CML with erythroblast phase
● Recurrent genetic abnormalities
● Secondary dyserythropoiesis


Pure erythroid leukemia (M6b)

General
=========================================================================

● Very rare (3% of acute erythroid leukemia cases)
● Also called erythemic myelosis, Di Guglielmo disease syndrome
● Aggressive
● Can be seen in infants
Enzyme cytochemistry: PAS (block-like staining pattern), alpha naphthyl acetate esterase (nonspecific esterase); also acid phosphatase
Prognosis: dismal, worse than erythroid / myeloid leukemia (AML-M6a)

Case reports
=========================================================================

● 51 year old man with pancytopenia (Arch Pathol Lab Med 2004;128:241)
● 58 year old man post-essential thrombocythemia (Am J Hematol 2004;77:140)
● 81 year old man post treatment for myeloma (Arch Pathol Lab Med 2006;130:1075)

Micro description
=========================================================================

● Committed exclusively to erythroid lineage (> 80% of BM cells) with no evidence of a significant myeloblastic component
● Usually proerythroblasts or early basophilic erythroblasts that are medium to large with deeply basophilic cytoplasm containing poorly demarcated vacuoles, often agranular
● Nuclei are round with fine chromatin and 1+ prominent nucleoli
● No apparent myeloid component

Micro images
=========================================================================


Bone marrow smear (Wright-Giemsa):
     
Pure erythroid leukemia  Very large erythroid precursors


Abnormal erythroid precursors at all stages of maturation, granulocyte lineage appears normal


Proerythroblasts and basophilic erythroblasts predominate, many have numerous cytoplasmic vacuoles


Three immature erythroblasts with large, clear cytoplasmic vacuoles


Erythroblasts are intermediate to large with round nuclei, fine chromatin and 1+ prominent nucleoli (fig A), cytoplasmic vacuoles are PAS+ (inset), bone marrow biopsy shows sheets of blasts and occasional multinucleated giant cells (fig B) and inset shows no staining for myeloperoxidase


Fig 1: large cells with deeply basophilic cytoplasm with vacuoles, round nuclei have fine chromatin and single distinct nucleoli; fig 2: PAS shows cytoplasmic block-like staining

Bone marrow biopsy:

Extensive replacement by immature erythroid precursors, with occasional very large abnormal cells

Stains:

Large abnormal cells and others are hemoglobin A+

Positive stains
=========================================================================

● Glycophorin A (mature forms), hemoglobin A, CD36, CD71, MDR1, P-glycoprotein (Mod Pathol 2000;13:407)
● Vacuoles are PAS+

Negative stains
=========================================================================

● Myeloperoxidase, CD13, CD33, CD34 (or weak), HLA-DR (or weak), CD41 and CD61
● Immature erythroblasts may be negative for hemoglobin A or glycophorin A

Molecular description
=========================================================================

● Often complex cytogenetics abnormalities involving #5 and #7

Differential diagnosis
=========================================================================

● AML-M0
● AML-M7
● AML-Myelodysplasia-Related Changes if 5 and 7 chromosomal abnormalities
● B/T ALL
● Congenital dyserythropoiesis
● Parvovirus infection
● Reactive erythroid hyperplasia associated with folate or vitamin B12 deficiency
● Undifferentiated leukemia



AML not otherwise categorized

Acute megakaryoblastic leukemia (AMKL, M7)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Up to 10% of AML in children, 5% or less of adult AML (Orphanet (May 2004))
● See also Myeloid leukemia associated with Down syndrome
● Associated with marrow fibrosis due to megakaryoblast secretion of fibrogenic cytokines, which makes marrow aspiration difficult
● In adults, median age 57 years, 59% have prior hematologic disorder or myelodysplastic syndrome (Blood 2006;107:880)
● 19% had prior chemotherapy, classify now as AML-MRC (myelodysplasia related changes) or t-AML
Survival: poor, median overall survival is 6 months
Peripheral blood: often contains micromegakaryocytes and atypical platelets
Down Syndrome (DS): 150x increased risk of AML compared to non-Down children age 0-4 years; 70% are AML M7 compared to 3-6% in non-Down children
● DS children ages 0-3 years: ALL vs AML risk is 1:1.2 compared to 4:1 for non-DS children

Clinical features
=========================================================================

● Thrombocytopenia, may have thrombocytosis, dysplastic features in neutrophils, erythroids, megakaryocytes and platelets
● Infrequent hepatosplenomegaly
● Associated with germ cell tumors in young boys

Diagnosis
=========================================================================

● WHO 2008: 20%+ blasts
● 50%+ blasts of megakaryocytic lineage are present in bone marrow
● Must exclude AML-MRC (myelodysplasia related changes), AML with t(1;22)(p13;q13); inv(3)(q21;q26.2); t(3;3)(q21;q26.2) and Down syndrome-related
● Megakaryocytic lineage is based on CD41+, CD61+ or positive platelet peroxidase reaction on EM

Case reports
=========================================================================

● 1 year old child with anemia and thrombocytopenia (Univ of Pittsburgh Case #439)
● Child with bi-allelic deletions within 13q14 and transient trisomy 21 with absence of GATA1 (Pediatr Blood Cancer 2011;57:516)
● Young boy with coexisting mediastinal germ cell tumor (Clin Transl Oncol 2007;9:329)
● 25 year old man with findings on FNA and CSF (Cytojournal 2011;8:17)
● 25 year old man with i(12p) related disease after primary mediastinal germ cell tumor (J Korean Med Sci 2011;26:1099)
● 58 year old woman with coexisting myeloid sarcoma of femur (Srp Arh Celok Lek 2011;139:805)
● Diagnosis 15 years after kidney transplantation (Ann Hematol 2011;90:843)
● "Cannibalistic" phagocytosis in acute megakaryoblastic leukemia (AML M7) with t(10;17)(p15;q22) (Leuk Lymphoma 2010;51:1944)
● Coexistence of meningeal infiltration and multiple lymphadenopathy as the initial presentation of de novo adult acute megakaryoblastic leukemia (Leuk Res 2011;35:e50)

Micro description
=========================================================================

● Megakaryoblasts (often better morphology on biopsy than smear) are medium / large cells with blue vacuolated, agranular, eosinophilic cytoplasm containing fine granules, cytoplasmic projections (blebs and pseudopods) resembling platelets, irregular cytoplasmic borders and cytoplasmic zoning; may occur in clusters
● Nuclei are round or slightly indented with finely reticular, dense chromatin and 1-3 nucleoli
● Myelofibrosis or increased marrow reticulin is common; may also have small lymphoid-like blasts

Micro images
=========================================================================

Bone marrow smears (Wright-Giemsa):

Blasts have abundant cytoplasm


Promegakaryocytes (larger than blasts, cytoplasmic budding, irregular nuclei, coarse chromatin) and large blasts


Touch prep shows 3 blasts with basophilic cytoplasm, coarse chromatin and distinct nucleoli

Bone marrow biopsy:

Extensive infiltration by blasts with sparse cytoplasm, frequent convoluted nuclei with fine chromatin and distinct nucleoli


Marked proliferation of megakaryocytes with variation in size and nuclear morphology

Stains:
               
CD61                                   (figures C, D)

          
Reticulin stain shows marked increase in reticulin fibers

          
CD34-red, podocalyxin-brown    CD42b (figure c)


PAS+ large megakaryocytes and micromegakaryocytes, also immature cells and erythrocyte precursors

Cytology images
=========================================================================



FNA and CSF

Positive stains
=========================================================================

● CD41 and CD61 (megakaryocyte specific), CD42b (Mod Pathol 2005;18:603), CD34, CD36, factor VIII and von Willebrand factor
● Variable CD13, CD33, CD71, alpha naphthyl acetate esterase, PAS and HLA-DR
● Rarely positive for alpha-1-antitrypsin, alpha-1-antichymotrypsin or lysozyme (Am J Surg Pathol 1987;11:883)

Negative stains
=========================================================================

● Myeloperoxidase, Sudan Black B, CD14, CD64 and glycophorin A

Electron microscopy description
=========================================================================

● Megakaryoblasts have demarcation membranes and “bulls-eye” alpha granules with peroxidase activity in nuclear envelope and endoplasmic reticulum, but not in granules and Golgi complex

Differential diagnosis
=========================================================================

ALL
AML-M0
● Blastic transformation of CML
AML-M1
AML-M5a
● Metastatic small blue cell tumors in children


Acute megakaryoblastic leukemia with t(1;22)(p13;q13); RBM15-MKL1

General
=========================================================================

● Uncommmon; <1% of AML; translocation appears to be specific to AMKL (Atlas of Genetics and Cytogenetics)
● WHO 2008: AML generally showing maturation in the megakaryocyte lineage, with indicated translocation, without Down syndrome
● Infants and young children (<3 years old), usually girls
● Most cases present within first month of life with marked hepatosplenomegaly (Blood 1991;78:748), prominent myelofibrosis, anemia, thrombocytopenia and moderately elevated WBC
● Tissue involvement resembles metastatic tumor
● Poor outcome (Leukemia 2000;14:216); but may respond well to intensive chemotherapy

Case reports
=========================================================================

● 1 month old infant with hepatic involvement and no initial marrow involvement (Pediatr Dev Pathol 2008;11:55)
● 9 month old girl with proliferation of erythroid and megakaryocytic lineages (Rinsho Ketsueki 1999;40:230)
● 59 year old man with RBM15-MKL1 (OTT-MAL) fusion transcript (Am J Hematol 2005;79:43)
● Hemophagocytosis by leukemic megakaryoblasts (J Pediatr Hematol Oncol 2012;34:576)

Micro description
=========================================================================

● Bone marrow is normocellular to hypercellular with prominent collagenous and reticulin fibrosis; blasts may be spindled and form intertwining bundles resembling metastatic disease (Am J Clin Pathol 1992;98:214)
● If <20% blasts on aspirate smear, check bone marrow for fibrosis which may mask blast count; if blasts are actually <20%, closely monitor for more definitive evidence of AML
● Small and large megakaryoblasts (medium to large with basophilic agranular cytoplasm, possibly with distinct blebs or pseudopods; round slightly irregular nuclei, fine reticular chromatin, one to three nucleoli), micromegakaryocytes, undifferentiated blasts, but no dyserythropoiesis and no dysgranulopoiesis

Micro images
=========================================================================



Various images

Positive stains
=========================================================================

● CD41+, CD61+ (cytoplasmic CD41 and CD61 more sensitive and specific), CD42+, CD36+; CD13 and CD33 may be positive

Negative stains
=========================================================================

● CD34, HLD-DR, CD45
● Cytochemistry: negative for Sudan Black and myeloperoxidase



AML not otherwise categorized

CD13, CD33 negative


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not part of WHO classification
● Usually AML M1 or M2
● Typical myeloid morphology and cytochemistry, but negative for CD13, CD14, CD33, CD61 and glycophorin (Am J Clin Pathol 2000;114:29)
● Elderly patients negative for CD33 and CD34 have poor prognosis (Cancer 2008;112:572)
● May express CD13 or CD33 at relapse (Rinsho Ketsueki 2001;42:314, Intern Med 1993;32:733)
Caution: may induce CD13 expression with in vitro culture (Southeast Asian J Trop Med Public Health 2002;33 Suppl 2:155)

Molecular description
=========================================================================

● Often t(8;21)(q22;q22) (Am J Clin Pathol 1997;107:68, Ann Hematol 1999;78:237)



AML not otherwise categorized

Acute basophilic leukemia


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Rare (< 1% of AML); tumor cells have basophilic differentiation
● Associated with marrow failure, circulating blasts, skin involvement, organomegaly, hyperhistaminemia symptoms and lytic lesions
Diagnosis: may require EM (Am J Clin Pathol 1991;96:160)
Enzyme cytochemistry: myeloperoxidase+ by EM but negative by light microscopy; acid phosphatase+; variable PAS+ in blocks and lakes; Sudan Black B-, non-specific esterase-
● Poor prognosis

Case reports
=========================================================================

● 18 year old man with 11q23 gene rearrangement (Indian J Pathol Microbiol 2007;50:443)
● 72 year old man with monosomy 7 as only abnormality (Cancer Genet Cytogenet 2007;172:168)
● Anaphylactoid reaction after chemotherapy and disseminated intravascular coagulation with massive pulmonary hemorrhage (Cancer 1995;75:110)

Treatment
=========================================================================

● Imatinib if bcr-abl present (Ann Biol Clin (Paris) 2006;64:361)

Micro description
=========================================================================

● Hypercellular marrow composed of medium sized blasts with high N/C ratio, moderate basophilic cytoplasm with variable number of coarse basophilic granules and cytoplasmic vacuoles
● Nucleus is round, oval or bilobed with 1-3 prominent nucleoli
● Occasional immature basophils; dysplastic erythroid features

Micro images
=========================================================================



Basophilic leukemia

Peripheral blood:

Immature basophilic precursors

Bone marrow smears:

Most blasts lack differentiation, but one blast has coarse azurophilic granules

Bone marrow biopsy:

Blasts and immature basophils with variable nuclear size and nucleoli; also plasma cells, endothelial cells and hemosiderophages

Stains:

Maturing basophils have metachromatic granules with toluidine blue stain

Positive stains
=========================================================================

● CD11b, CD13, CD33, CD34, CD123, CD203c (Eur J Clin Invest 2001;31:894)
● Toluidine blue (metachromatic granules), HLA-DR; variable CD9, membranous CD22 and TdT

Negative stains
=========================================================================

● Myeloperoxidase by light microscopy
● CD117-, tryptase- and CD25- distinguish from mast cell leukemia

Molecular description
=========================================================================

● No specific findings; cases with t(6;9)(p23;q34) and with BCR-ABL1 are excluded

Electron microscopy description
=========================================================================

● Coexistance of basophilic granules and immature mast cell granules

Electron microscopy images
=========================================================================



Granules contain amorphous speckled substance, one granule has a myelin figure

Differential diagnosis
=========================================================================

AML-M0 - EM shows no basophilic granules
AML-M2 subtypes with basophilia: see Am J Hematol 2004;76:134
● Acute eosinophilic leukemia
ALL with coarse granules
● CML in blast crisis
● Mast cell leukemia



AML not otherwise categorized

Myeloid sarcoma


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Extramedullary tumor mass of neoplastic immature myeloid (granulocytic or monocytic) cells
● Also called extramedullary myeloid tumor, granulocytic sarcoma, chloroma
● See also descriptions in various chapters
● Often misdiagnosed, particularly without immunostains
● Present in 2-8% of AML patients; prognosis is that of underlying leukemia
● Equivalent to blast transformation in setting of myelodysplastic syndrome or myeloproliferative disease (Korean J Lab Med 2006;26:143)
● Usually associated with AML M4 or M5 (M4e or M5a in children), CML, chronic idiopathic myelofibrosis, hypereosinophilic syndrome or polycythemia vera
● Rarely no leukemia / myelodysplasia is identified in blood or bone marrow (J Neurosurg 2006;105:916)
Common sites: lymph nodes, subperiosteal bone, skin, orbit, spinal canal and mediastinum

Case reports
=========================================================================

● 27 year old woman with punched-out, lytic, intramedullary lesion in fibula (Case of the Week #130)

Treatment
=========================================================================

● Aggressive treatment recommended (Leukemia 2007;21:340, Cancer 2002;94:1739)
● Usually evolves to AML or has additional tumor masses at other sites

Gross images
=========================================================================



Kidney tumor   Bone tumor

Micro description
=========================================================================

Blastic type: myeloblasts with mild / moderate rim of basophilic cytoplasm, fine nuclear chromatin, 2-4 nucleoli
Immature type: myeloblasts, promyelocytes, eosinophilic myelocytes
Differentiated type: promyelocytes, eosinophilic myelocytes and more mature forms; rarely crystalline inclusions similar to Charcot-Leyden crystals (Arch Pathol Lab Med 2002;126:85)

Micro images
=========================================================================


                
Differentiated (left) versus blastic       Various images
types (center and right)-site unknown

Lymph node:
            
Cells have fine chromatin resembling     Large blast cells resemble large cell lymphoma,
lymphoblastic lymphoma          also some eosinophilic myelocytes

            
Tumor cells have irregularly        Resembles lymphoblastic lymphoma,
folded and convoluted nuclei        but has cytoplasmic granules and distinct nuclei

            
Many tumor cells have azurophilic     Tumor cells mix with residual normal lymphocytes
granules


Immature cells with moderate to abundant cytoplasm,
round / oval nuclei, distinct and prominent nucleoli and immature eosinophils


Lymph node has prominent eosinophilic myelocytes and blasts

Case of the week #130 (bone):
               
                                       CD45 / LCA

           
CD45RO      CD3        CD34       CD20

Other:

Anorectal ulcer

       
Appendix

       
Breast                 Has blasts with numerous azurophilic granules
                    and promyelocytes, classified as AML with maturation

   
Bladder       Skin-eosinophilic myelocytes and blasts

   
Small intestine


Orbital mass with t(8;21) has blasts with immature eosinophils

            
Soft tissue of paracervical        Spinal dura-some tumor cells
spine (H&E and CD99)          have cytoplasmic granules


Testes

Stains:
           
Myeloperoxidase: Lymph node     Mediastinum   Breast (left), CD43 (right)


Skin: various stains

   
CD68: Spine    Uterus

       
Chloroacetate esterase - lymph node     Lysozyme - orbit

Cytology description
=========================================================================

● Usually background lymphoglandular bodies
● Auer rods and eosinophilic myelocytes are rare
● Resembles large cell lymphoma (Cancer 2000;90:364)

Cytology images
=========================================================================



Breast: has blasts with numerous azurophilic granules and promyelocytes, classified as AML with maturation

Positive stains
=========================================================================

Almost all tumors: lysozyme and CD43
Myeloid tumors: myeloperoxidase and CD117
Myeloblasts: CD13, CD33 (Arch Pathol Lab Med 2001;125:1448)
Monocytic tumors: CD68 and variable CD163 (Am J Clin Pathol 2004;122:794)
Monoblasts: CD11c (Diagn Pathol 2007;2:42), CD14, CD56 (Am J Clin Pathol 2000;114:807), CD99 (55%, Mod Pathol 2000;13:452), HLA-DR and chloroacetate esterase (Ann Saudi Med 2001;21:287)
Other: CD4, CD34 and TdT

Negative stains
=========================================================================

● CD3, CD20, CD34 and CD79a

Molecular description
=========================================================================

● Most common are monosomy 7 (11%), trisomy 8 (10%) and MLL rearrangements (9%)
● Also inv(16), trisomy 4, monosomy 16, 16q-, 5q-, 20q-, trisomy 11, t(8;21)(q22;q22) in pediatric cases and NPM1 mutations (16%)

Differential diagnosis
=========================================================================

Burkitt lymphoma
● Poorly differentiated lymphoma
● Small round cell tumors


Myeloid sarcoma of female genital tract
=========================================================================

● Rare, but may be initial clinical presentation
● Usually ovary, also vagina and cervix (Am J Surg Pathol 1997;21:1156, Am J Clin Pathol 2006;125:783)
● Mean age 40 years, range 13-76 years
Enzyme cytochemistry: chloroacetate esterase, lysozyme, myeloperoxidase, CD43, CD68, CD117

Micro description
=========================================================================

● Usually diffuse growth pattern, also cords and pseudoacinar spaces; sclerosis common

Micro images
=========================================================================



Left to right: Pelvic mass (various images), uterus (various images)

Differential diagnosis
=========================================================================

● Carcinoma
● Granulosa cell tumor
● Lymphoma



AML not otherwise categorized

Acute panmyelosis with myelofibrosis


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Also called acute (malignant) myelofibrosis, acute (malignant) myelosclerosis, acute myelodysplasia with myelofibrosis
● Now a distinct entity in WHO (2008), but not previously (Ann Hematol 2004;83:513, Leuk Lymphoma 2004;45:681)
● Rare, rapid onset, aggressive, usually adults
● Weakness, fatigue, fever, bone pain, pancytopenia; usually no marked splenomegaly
● Median survival is 2-9 months

Case reports
=========================================================================

● Successful treatment with biphosphonates (Eur J Haematol 2004;73:215)

Micro description
=========================================================================

● Hypercellular marrow with erythroblasts, immature granulocytes, megakaryocytes
● Prominent megakaryocytic abnormalities with variation in size and dysplastic changes, immature granulocytes with dysplasia and immature erythrocytes
● Usually marked fibrosis (reticulin > collagen)
● Aspirate smear is often hypocellular due to marked fibrosis

Micro images
=========================================================================


Bone marrow smear (Wright-Giemsa):
              
Numerous blasts, some CD61+,         Various images
also abnormal erythroid and granulocyte cells


Blasts and more mature granulocytes, also a large megakaryocyte with
a poorly lobulated nucleus and dispersed chromatin,
occasional neutrophils and late stage erythroblasts

Bone marrow biopsy:
              
Partial replacement of marrow by        Numerous blasts with some clustering
blasts and increased fibrous tissue

Lymph node biopsy:
              
Total effacement by blasts, also scattered     Blasts have fine chromatin and small but
megakaryocytes at various stages of     distinct nucleoli, mitotic figures are present
maturation

Site unspecified:

Acute panmyelosis with myelofibrosis

Stains:
              
Increase in coarse reticulin fibers        Reticulin stain shows markedly hypercellular marrow
                        with proliferation of blasts and maturing cells,
                        and increase in coarse reticulin fibers

Positive stains
=========================================================================

● CD34 and HLA-DR (Leuk Lymphoma 2004;45:1873)
Erythroblasts: glycophorin A, hemoglobin A
Granulocytes: myeloperoxidase, CD13, CD33 and CD117
Monocytes: lysozyme, CD68
Megakaryocytes: CD31, CD41, CD61, PAS and factor VIII

Negative stains
=========================================================================

● Usually CD42b (Mod Pathol 2005;18:603), von Willebrand factor

Differential diagnosis
=========================================================================

Acute megakaryoblastic leukemia: no prominent changes in granulocytes or erythroid cells
Chronic idiopathic myelofibrosis: marked splenomegaly and prominent dysplasia
● Metastatic carcinoma with desmoplasia
Myelodysplastic syndrome with myelofibrosis: lacks high percentage of blasts



AML not otherwise categorized

AML with Philadelphia chromosome


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not part of WHO classification
● 1% of AML (Leuk Res 2004;28:579, Zhongguo Shi Yan Xue Ye Xue Za Zhi 2005;13:358), more common in bilineal, biphenotypic and acute basophilic leukemias
● Rarely is a secondary cytogenetic abnormality (Cancer Genet Cytogenet 2006;165:70)
● Compared to CML in blast crisis, has less frequent splenomegaly and peripheral basophilia, lower marrow cellularity and lower M/E ratios in marrow (Am J Clin Pathol 2007;127:642)
● Median survival 9 months
● Associated with poor prognosis in biphenotypic leukemia (Haematologica 1999;84:699)
● Philadelphia chromosome / translocation is t(9;22)(q34;q11), associated with CML (Wikipedia (Philadelphia chromosome))

Case reports
=========================================================================

● 44 year old man with dual presence of t(9;22) and inv(16) (Am J Clin Pathol 2006;125:260)
● Positive AML-M7 with extreme thrombocytosis and resistance to therapy (Ann Hematol 2004;83:381)

Treatment
=========================================================================

● Possibly imatinib, then allogeneic stem cell transplant (Eur J Haematol 2007;79:170)

Micro description
=========================================================================

● May occur in various AML subtypes

Micro images
=========================================================================



Fig A: hypercellular marrow (80%); fig B: mild increase in reticulin
Fig C: erythroid cells are dysplastic; fig D: CML




AML not otherwise categorized

AML with pseudo-Chèdiak-Higashi anomaly


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not part of WHO classification
● Frequent in acute promyelocytic leukemia; up to 25% of AML-M2 (Acta Paediatr Jpn 1990;32:651)
● Giant granules may be due to fusion of primary granules or small dense vesicles
● See also Bone marrow-nonneoplastic chapter

Case reports
=========================================================================

● 16 year old girl with AML-M5a and t(10;11) (Clin Lab Haematol 2000;22:303)

Micro description
=========================================================================

● Giant cytoplasmic granules

Micro images
=========================================================================


       
Specific granules resemble Chediak-Higashi anomaly


In blast cells in AML-M2 patients


Giant inclusion bodies in bone marrow of patient with Chediak-Higashi syndrome, for comparison

Positive stains
=========================================================================

● CD2 (Am J Clin Pathol 2006;125:791)

Molecular description
=========================================================================

● May be associated with double minutes (Leukemia 2002;16:152)

Electron microscopy description
=========================================================================

● Peroxidase positive granules with a dense matrix but no obvious crystalline structure, may contain membranous lamellae or tubular structures (Cancer Res 1980;40:4473, Sangre (Barc) 1994;39:135)



AML not otherwise categorized

Hypocellular AML


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Defined as < 20% bone marrow cellularity, 20% or more are blasts (WHO); other definitions range up to 40% cellularity
● Up to 10% of AML cases
● Median age 67 years (Leuk Res 1996;20:563)
● Rare blasts in peripheral blood
● Often has smoldering course, although intensive chemotherapy may cause complete remission

Case reports
=========================================================================

● 78 year old man and woman with minimally differentiated hypoplastic leukemia (Nihon Ronen Igakkai Zasshi 1997;34:70)

Micro images
=========================================================================


                 
Markedly hypocellular marrow in 57 year old man  Cells in interstitium are predominantly blasts
with severe pancytopenia and rare blasts in blood

Positive stains
=========================================================================

● CD34, CD117, myeloperoxidase

Differential diagnosis
=========================================================================

● Aplastic anemia: no excess blasts, interstitial bone marrow cells are plasma cells, lymphocytes and mast cells, not blasts
Refractory anemia with excess blasts
● Substance abuse: see Arch Pathol Lab Med 2005;129:e35



Acute lymphoblastic leukemia (ALL) - general


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 6050 cases/year in US in 2012 (National Cancer Institute), peaks at age 4; usually age 15 years or less
● 80% of childhood leukemia is ALL
● Higher incidence in whites, males and advanced (not developing) countries
● 85% are B cell, 15% are T cell, but both often express aberrant myeloid or lymphoid associated antigens
● Note that only 10-20% of lymphoblastic lymphoma is B cell lineage
Risk factors: in utero radiation, Down syndrome, ataxia telangiectasia, but most cases have no known cause
Symptoms: abrupt stormy onset, symptoms related to bone marrow depression (fatigue, fever, bleeding), bone pain and tenderness (due to marrow expansion), joint pain, generalized lymphadenopathy, hepatosplenomegaly, testicular involvement, CNS manifestations
Atypical presentation: hypercalcemia, bone lesions and no circulating blasts
Laboratory: anemia common, platelet count < 100K in 75% and < 10K in 15%; leukopenia (25%), WBC > 100K (10%)
Diagnosis: immunostains required for diagnosis
Relapse: blasts usually unchanged; may progress from L1 to L2, TdT positive to negative (25%), gain or lose an antigen (CD10, HLA-DR), evolve clonally (75%) or evolve to AML; CNS relapse common

Prognostic features
=========================================================================

● Cytogenetics / FISH is single most important prognostic factor for adults (Blood 2008;111:2563)
Favorable prognosis: age 1-10 years, female, white; preB phenotype, hyperdiploidy > 50, t(12,21), normal WBC count at presentation, non-traumatic tap with no blasts, rapid response to chemotherapy, CD10+
Intermediate prognosis: hyperdiploidy 47-50, diploid, 6q- and rearrangements of 8q24
Unfavorable prognosis: under age 2 (usually have 11q23 translocations) or over age 10; t(9;22) (but not if age 59+ years, Am J Clin Pathol 2002;117:716); male, > 50x108/L, hypodiploidy, near tetraploidy, 17p-, MLL rearrangements and t(v;11q23); CD10- preB ALL; non-traumatic tap with > 5% blasts or traumatic tap with 7%+ blasts, also increased microvessel staining using CD105 in children (Leuk Res 2007;31:1741), MDR1 expression in children (Oncol Rep 2004;12:1201) or adults (Blood 2002;100:974)

Case reports
=========================================================================

● Mature phenotype but non-L3 morphology (Mod Pathol 2004;17:832)

Treatment
=========================================================================

Children: multiagent chemotherapy plus CNS chemotherapy; 90% go into remission, 2/3 are cured; thrombopoietin may induce CML like changes (Am J Clin Pathol 2002;117:844)
Adults: choice of chemotherapy or stem cell transplantation is not clear (Hematology Am Soc Hematol Educ Program 2007:444)

Micro description
=========================================================================

● Blasts have scant agranular cytoplasm, no Auer rods, coarse to fine chromatin, often indistinct nucleoli and no dysplastic myeloid cells
Peripheral smear: leukoerythroblastosis common with granulocyte precursors and nucleated RBCs, lymphoblasts, occasionally reactive lymphocytes and rarely marked eosinophilia
Bone marrow: hypercellular, high percentage of lymphoblasts
Children: 80% are L1, 10-20% L2 and < 5% L3
Adults: 35% are L1, 60% L2 and < 5% L3

Micro images
=========================================================================


Peripheral smear images:

Blasts with scant cytoplasm and prominent nucleoli

L1 type (blood smears):
                
Blasts have minimal cytoplasm, variable nuclear   Blasts have moderate cytoplasm, round nuclei of variable size,
size and chromatin density, irregular nuclear    coarse chromatin and some resemble mature lymphocytes
contour, some small nucleoli

L1 type (bone marrow smears):

Left: blasts contain large cytoplasmic azurophilic granules (uncommon), but were B cells by IHC and cytochemistry
Right: classic morphology and stains


L1 type (bone marrow biopsy):
                      
Markedly hypercellular marrow with   Lymphoblasts occupy marrow, have    Lymphoblasts are small with more
lymphoblasts replacing normal      minimal cytoplasm and indistinct cell  condensed chromatin
marrow elements           borders, convoluted nuclei, angulated
                    borders


Marrow contains lymphoblasts, one megakaryocyte,
normoblasts in upper half and occasional eosinophils
and eosinophil precursors

L1 type (stains):

Lymphoblasts have block and coarse granular PAS staining

L2 type (blood smears):
                        
Three large lymphoblasts have    Lymphoblasts have variable size, moderate Most lymphoblasts have variable size,
moderate cytoplasm, large nuclei   cytoplasm, markedly irregular nuclei with  reticular chromatin with prominent
with coarsely reticular chromatin   coarse chromatin and distinct nucleoli     nucleoli and some have L1 features
and 1-3 prominent nucleoli


Classic morphology


Blasts have cytoplasmic azurophilic granules (uncommon)

L2 type (bone marrow smears):

Large lymphoblasts with cytoplasm that has numerous,
sharply defined clear vacuoles similar to L3, non-L3
features are reticular chromatin, prominent nucleoli, TdT+ and CD10+

L2 type (bone marrow biopsy):

Relatively large lymphoblasts with variable nuclear shape, dispersed chromatin and prominent nucleoli

L3 type (bone marrow smears):

Classic morphology


No prominent vacuoles, dispersed chromatin and
more obvious nucleoli than usually observed in L3,
diagnosed as ALL-L3 and non-Burkitt’s type

L3 type (stains):

Strong cytoplasmic staining by methyl green pyronine (left),
vacuoles are Oil Red O positive (right)


Unusual case with high myeloperoxidase activity

Other:

Relapsed ALL

Enzyme cytochemistry
=========================================================================

● Negative for myeloperoxidase, chloroacetate esterase, non-specific esterase (usually) and only rarely positive for Sudan Black B (Mod Pathol 1992;5:68)
● Positive for PAS (75%, coarse clumping corresponds to glycogen), acid phosphatase (T-ALL has focal paranuclear staining)
● Only L3 stains for glycogen with Sudan Black B and PAS

Positive stains
=========================================================================

● CD99 (MIC2), TdT, bcl2 and CD34

Negative stains
=========================================================================

● Myeloperoxidase (usually, but positive in 23% of adults using a polyclonal antibody, Am J Clin Pathol 2001;116:25)
Note: TdT negative cases may demonstrate early T-cell lineage by flow cytometry (Arch Pathol Lab Med 2000;124:92)

Molecular description
=========================================================================

● 90% have cytogenetic abnormalities, usually hyperdiploidy (> 50 chromosomes), also pseudodiploidy (46 chromosomes but structural anomalies), t(12,21); t(9,22) [Philadelphia chromosome] and t(4,11)

Electron microscopy images
=========================================================================


L1 type:

Cytoplasm has small mitochondria, small Golgi region, scattered polyribosomes and
occasional strands of round endoplasmic reticulum, nucleus is indented with a small
nucleolus, chromatin is condensed and concentrated at nuclear periphery

L2 type:

Large lymphoblast with moderate cytoplasm, dispersed chromatin
with peripheral condensation and large prominent nucleolus

L3 type:

Abundant cytoplasm with numerous polyribosomes and large lipid vacuoles (arrow)
nuclei have peripherally condensed chromatin and 1+ prominent nucleoli

Differential diagnosis
=========================================================================

Adult T cell leukemia
AML
AML-M3
CLL
Hematogones - normal B lymphoid precursors (Am J Clin Pathol 2000;114:66)
● Hypoplastic anemia
Merkel cell carcinoma - may be TdT+ (Mod Pathol 2007;20:1113)
Non-Hodgkin’s lymphoma
● Reactive lymphocytosis



ALL - WHO classification


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● WHO classification system includes former FAB classifications ALL-L1 and L2
● FAB L3 is now considered Burkitt lymphoma


WHO classification of acute lymphoblastic leukemia
=========================================================================

Precursor B lymphoblastic leukemia / lymphoblastic lymphoma:
● ALL with t(9;22)(q34;q11.2); BCR-ABL (Philadelphia chromosome)
● ALL with t(v;11q23) (MLL rearranged)
● ALL with t(1;19)(q23;p13.3); TCF3-PBX1 (E2A-PBX1)
● ALL with t(12;21)(p13;q22); ETV6-RUNX1 (TEL-AML1)
● Hyperdiploid > 50
● Hypodiploid
● t(5;14)(q31;q32); IL3-IGH

Precursor T lymphoblastic leukemia / lymphoma

Additional references
=========================================================================

Mod Pathol 2000;13:193


FAB classification of acute lymphoblastic leukemia
=========================================================================

● Terminology now considered to not be relevant because L1 and L2 morphology do not predict immunophenotype, genetic abnormalities or clinical behavior
L1: small cells, scant basophilic cytoplasm with variable vacuoles, small nucleoli, regular nuclear shape and homogenous chromatin
L2: large heterogeneous cells with moderate cytoplasm, often intensely basophilic, variable vacuoles; large nucleoli, irregular nuclear shape with clefting and indentation, large nucleoli and variable nuclear chromatin
L3: medium to large homogenous cells with moderate cytoplasm that is intensely basophilic with prominent cytoplasmic vacuoles; at least one prominent nucleoli (may be 2-4), round to oval nucleus, finely stippled homogenous chromatin, cytologically identical to Burkitt’s and Burkitt’s like lymphoma (small noncleaved); has mature phenotype (i.e. expresses surface immunoglobulin); fat vacuoles are Sudan black+, Oil red O+ and PAS -; cytoplasm is methyl green-pyronine positive



ALL with eosinophilia


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Not part of WHO classification
● ALL with marked eosinophilia is rare (< 50 cases reported through 2005), but may obscure ALL diagnosis
● Symptoms are related to hypereosinophilia, including respiratory failure, myocardial infarction and cerebrovascular accident (Leuk Lymphoma 2005;46:1045)
● Eosinophilia resolves with remission, returns with relapse
● Eosinophilia is usually reactive, not part of leukemic cells

Case reports
=========================================================================

● 5 year old girl with 5q- deletion (Pediatr Dev Pathol 2003;6:558)
● 8 year old boy with t(5;9) and detection of residual disease in CSF by PCR (Arch Pathol Lab Med 2003;127:601)
● 10 year old girl with urticaria and hypereosinophilia (J Am Acad Dermatol 2004;51(5 Suppl):S151)
● 44 year old man with prior eosinophilic myelodysplasia (J Clin Pathol 1999;52:388)
● Young boy with T-ALL with eosinophilia and AML (Cytometry B Clin Cytom 2005;65:37)
● Prior idiopathic hypereosinophilic syndrome (Leuk Res 2005;29:975)

Treatment
=========================================================================

● Steroids suppress eosinophlia

Micro images
=========================================================================



Bone marrow smear shows blasts, eosinophilic myelocytes, granulocytes and normoblasts


CSF shows prominent eosinophilia, basophilia and rare blasts (center)

Molecular description
=========================================================================

● May have t(5;14)(q31;q32) - IL3 and IgH (Atlas of Genetics and Cytogenetics)



PreB ALL

B cell acute lymphoblastic leukemia (ALL) / lymphoblastic lymphoma (LBL)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Current 2008 WHO classification: B lymphoblastic leukemia / lymphoma, NOS or B lymphoblastic leukemia / lymphoma with recurrent genetic abnormalities
● See also lymphomas: B cell chapter
● Also called B cell acute lymphoblastic leukemia / lymphoblastic lymphoma, pre B ALL / LBL
● Usually children
● B acute lymphoblastic leukemia presents with pancytopenia due to extensive marrow involvement, stormy onset of symptoms, bone pain due to marrow expansion, hepatosplenomegaly due to neoplastic infiltration, CNS symptoms due to meningeal spread and testicular involvement
● B acute lymphoblastic lymphoma often presents with cutaneous nodules, bone or nodal involvement, < 25% lymphoblasts in bone marrow and peripheral blood; aleukemic cases are usually asymptomatic
● Depending on specific leukemia, arises in either hematopoietic stem cell or B-cell progenitor
● Tumors are derived from pre-germinal center naive B cells with unmutated VH region genes
● Have multiple immunophenotyping aberrancies relative to normal B cell precursors (hematogones); at relapse, 73% show loss of 1+ aberrance and 60% show new aberrancies (Am J Clin Pathol 2007;127:39)

Prognostic features
=========================================================================

● Favorable prognosis: age 1-10 years, female, white; preB phenotype, hyperdiploidy>50, t(12,21), WBC count at presentation <50x108/L, non-traumatic tap with no blasts in CNS, rapid response to chemotherapy < 5% blasts on morphology on day 15, remission status after induction <5% blasts on morphology and <0.01% blast on flow or PCR, CD10+
● Intermediate prognosis: hyperdiploidy 47-50, diploid, 6q- and rearrangements of 8q24
● Unfavorable prognosis: under age 1 (usually have 11q23 translocations) or over age 10; t(9;22) (but not if age 59+ years, Am J Clin Pathol 2002;117:716); male, > 50x108/L WBC at presentation, hypodiploidy, near tetraploidy, 17p- and MLL rearrangements t(v;11q23); CD10-; non-traumatic tap with > 5% blasts or traumatic tap (7%); also increased microvessel staining using CD105 in children (Leuk Res 2007;31:1741), MDR1 expression in children (Oncol Rep 2004;12:1201) and adults (Blood 2002;100:974), 25%+ blasts on morphology on day 15, remission status after induction ≥ 5% blasts on morphology and ≥ 0.1% blasts on flow or PCR

Case reports
=========================================================================

● 12 month old girl and 13 month old boy with mature phenotype but no translocations (Arch Pathol Lab Med 2003;127:1340)
● 56 year old man with ALL arising from follicular lymphoma (Arch Pathol Lab Med 2002;126:997)
● 76 year old man with basal cell carcinoma (Diagn Pathol 2007;2:32)
● With hemophagocytic lymphohistiocytosis (Pediatr Blood Cancer 2008;50:381)

Treatment
=========================================================================

● Chemotherapy cures more children than adults; adolescents benefit from intensive regimens (Hematology Am Soc Hematol Educ Program 2005:123)

Micro description
=========================================================================

Bone marrow smears: small to intermediate blast-like cells with scant, variably basophilic cytoplasm, round / oval or convoluted nuclei, fine chromatin and indistinct nucleoli; frequent mitotic figures; may have “starry sky” appearance similar to Burkitt lymphoma; may have large lymphoblasts with 1-4 prominent nucleoli resembling myeloblasts; usually no sclerosis
Bone marrow biopsy: usually markedly hypercellular with reduction of trilinear maturation; cells have minimal cytoplasm, medium sized nuclei that are often convoluted, moderately dense chromatin and indistinct nucleoli, brisk mitotic activity
Other tissues: may have “starry sky” appearance similar to Burkitt lymphoma; collagen dissection, periadipocyte growth pattern and single cell linear filing

Micro images
=========================================================================


Peripheral blood:
             
Blasts with scant cytoplasm  Blasts have L1 morphology,  L1 type has smaller blasts with minimal cytoplasm,
but prominent nucleoli       but mature phenotype      coarse chromatin, some cleaved nuclei or irregular
                              contours and no distinct nucleoli

Lymphoblastic lymphoma:
      
TdT negative cases     Figure a: H&E; b: CD179b; c/d: CD179a
              (FF is frozen tissue, PF is paraffin fixed)

Lymphoblastic lymphoma with basal cell carcinoma:
               
                       TdT+          CD79a+        CD34+

Kidney involvement

19 year old man with hypertension and renal insufficiency

Positive stains
=========================================================================

● TdT (negative in 3%, Am J Clin Pathol 2004;121:810), CD19, CD22, CD79a, PAX5
● CD34 (75%), usually cytoplasmic (not surface) immunoglobulin, but rarely surface immunoglobulin (Am J Clin Pathol 2004;121:512)
● Also CD9, CD24, CD38, CD45 and HLA-DR; variable CD10 and CD20 (Blood 2006;108:3302)
● Myeloid antigens CD13 or CD33 in 27% (Exp Mol Pathol 2007;83:471), particularly pediatric cases with Philadelphia chromosome or 11q23 rearrangements (Am J Clin Pathol 1999;111:467)

Negative stains
=========================================================================

● Surface IgM, CD15, CD30

Flow cytometry images
=========================================================================



Patient with relapse of precursor B-ALL illustrating multiple antigenic aberrancies

Molecular description
=========================================================================

● Usually chromosomal abnormalities

Differential diagnosis
=========================================================================

Based on morphology:
AML - prominent nucleoli, delicate chromatin and fine azurophilic cytoplasmic granules
Blastic variant of mantle cell lymphoma
Burkitt lymphoma
Ewing sarcoma: negative for CD79a, CD43, TdT and immunoglobulin or T cell receptor rearrangement, vimentin++
Granulocytic sarcoma
Hodgkin lymphoma



PreB ALL

B lymphoblastic leukemia / lymphoma with t(9;22)(q34;q11); BCR-ABL1


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● ALL with BCR-ABL1 fusion transcript (Philadelphia chromosome)
● 30% of adults with ALL, 4% of children but 80% of infants
● Excluding infants, older age and higher WBC at presentation than other B ALL
● May have more organomegaly or CNS involvement than other B ALL
● Poor prognosis

Treatment
=========================================================================

● Tyrosine kinase inhibitors (Imatinib) cause some complete responses (Cancer 2007;110:1178), but change in overall survival is minimal (Cancer 2007;109:2068, Hematology Am Soc Hematol Educ Program 2007:435)

Micro description
=========================================================================

● No defining morphology, but large blasts with prominent nucleoli and cytoplasmic granules are more common than other B ALL

Micro images
=========================================================================



Leukemic cells resemble early erythroblasts

Cytology images
=========================================================================



CSF-Contributed by Dr. Julia Braza, Beth Israel Deaconess Medical Center, Boston, Massachusetts (USA)

Positive stains
=========================================================================

● Myeloid antigens in 71% (Am J Clin Pathol 1999;111:467)

Flow cytometry images
=========================================================================



B-ALL associated with t(9;22); lymphoblasts express B-lineage markers CD19, CD20, CD22, immature markers CD34, TdT, CD10, and aberrant CD25. They are aberrantly dim for CD38 and CD81. This pattern is useful in identifying minimal residual disease

Molecular description
=========================================================================

● Translocation involves abl on #9q34 (tyrosine kinase) and bcr on #22q11 (breakpoint cluster region)
● Most childhood cases associated with p190 kd BCR-ABL1 fusion protein
● In 50% of adults, has p210 kd fusion protein that is present in CML, the rest is p190 kd; no definitive clinical difference

Molecular images
=========================================================================


     
Drawing of translocation  Karyotype


FISH-Contributed by Dr. Julia Braza, Beth Israel Deaconess Medical Center, Boston, Massachusetts (USA)



PreB ALL

B lymphoblastic leukemia / lymphoma with t(v;11q23); MLL rearranged


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Rearrangements of MLL gene
● 20% of ALL overall (Anticancer Res 2005;25:1931), including 80% of infants (Leukemia 2007;21:633), 10% of older children and adults
● May have bilineal lymphoblasts, with monoblasts and promonocytes
● Usually infants < 1 year with markedly increased WBC (> 100x109/L), CNS involvement; pure lymphomatous involvement not typical
● Poor prognosis (30% event free survival)

Treatment
=========================================================================

● Intensive chemotherapy followed by hematopoietic stem cell transplantation

Micro description
=========================================================================

● No defining morphology

Positive stains
=========================================================================

● TdT, CD19, CD34 and HLA-DR
● Also CD15, often myeloid antigens CD13 and CD33 (Am J Clin Pathol 1999;111:467)

Negative stains
=========================================================================

● CD10

Molecular description
=========================================================================

● Over 75 genetic arrangements; most translocations at 11q23 involve MLL (mixed lineage leukemia) gene
● t(4;11)(q21;q23) - MLL-AF4: occurs in 60% of infants, 2% of other children and 3-6% of adults
● t(11;19)(q23;p13.3) - MLL-ENL and others
● MLL translocation is associated with FLT3 overexpression
● 11q23 deletions are NOT included in this group because different immunophenotype, clinical and prognostic features

Molecular images
=========================================================================



Diagram of ALL1 / MLL duplication



PreB ALL

B lymphoblastic leukemia / lymphoma with t(1;19)(q23;p13.3); E2A-PBX1 (TCF3-PBX1)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 5-6% of ALL; commonly detected by conventional cytogenetics in children
● E2A-PBX1 (TCF3-PBX1) is chimeric gene formed by t(1;19)(q23;p13.3) (Mol Cell Biol 1994;14:3938)
● High WBC counts, frequent CNS involvement
● In children (Blood 1984;63:721) and adults (Haematologica 2010;95:241), is no longer a poor prognostic factor, due to intensive therapy and bone marrow transplantation

Case reports
=========================================================================

● Child with t(1;19) without fusion transcript by PCR or Southern blot (Rinsho Ketsueki 2005;46:7)

Micro description
=========================================================================

● No distinct morphologic findings

Positive stains
=========================================================================

● Typical immunophenotype cytoplasmic µ (cµ), CD10, CD19
● If cytoplasmic µ negative, can be suspected if strong CD9 and CD34-

Molecular description
=========================================================================

● Produces fusion transcript of PBX1 and E2A; occurs in balanced and unbalanced forms; unbalanced form is der(19)t(1;19)
● The reciprocal product of der(1)t(1;19) is lost and the normal chromosome 1 is duplicated (Leukemia 2001;15:95, Atlas of Genetics and Cytogenetics in Oncology and Haematology)

Notes:
● “Unbalanced translocations” means the exchange of chromosomal material is unequal, resulting in extra or missing genes
● “der” means derivative chromosome - term is used when only one chromosome from a translocation is present, or when one chromosome has two or more structural abnormalities

Molecular images
=========================================================================


   
Karyotype (unbalanced) with loss of der(1)t(1;19)



PreB ALL

B lymphoblastic leukemia / lymphoma with t(5;14)(q31;q32); IL3-IGH


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Diagnosis based on immunophenotype and genetic findings, even with low blast count
● Very rare; < 1% of all ALL; both children and adults (Blood 1989;73:2081)
● Presents with variable eosinophilia; may be asymptomatic and lack any blasts (Medicine (Baltimore) 1990;69:232)

Case reports
=========================================================================

● 13 year old boy with cardiac disease (BMJ Case Rep 2012 Jan 20;2012)
● CD10+ acute leukemia with t(5q;14q) translocation and hypereosinophilia (Acta Haematol 1989;82:85)

Micro description
=========================================================================

● CD19+ CD10+ lymphoblasts with circulating reactive eosinophils

Micro images
=========================================================================



Reactive eosinophilia in ALL patient

Molecular description
=========================================================================

● t(5;14)(q31;q32); IL3-IGH (Atlas Genet Cytogenet Oncol Haematol September 2011)



PreB ALL

B lymphoblastic leukemia / lymphoma with t(12;21)(p13;q22); TEL-AML1 (ETV6-RUNX1)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 17 January 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● 20-30% of childhood preB ALL; most common translocation (Chin Med J (Engl) 2003;116:1298, Atlas of Genetics and Cytogenetics in Oncology and Haematology), but not infants; also 3% of adults
● 5 different patterns of gene expression involving 14 genes, can detect with gene chip (BMC Genomics 2007;8:385)
● Excellent prognosis due to good response to chemotherapy; 90% remissions; relapses occur later than other ALL
● Persistence of TEL-AML1 transcripts is not necessarily related to relapse (Pediatr Int 2003;45:275)

Micro description
=========================================================================

● No distinct morphology

Positive stains
=========================================================================

● CD10 (bright), CD19, CD34, HLA-DR
● Also CD13 and CD33 (Diagn Mol Pathol 2000;9:184)

Negative stains
=========================================================================

● CD9, CD20

Molecular description
=========================================================================

● Fusion of TEL/ETV6 and AML1/RUNX1/CBFA2 genes
● Detect with FISH or PCR; not found by conventional cytogenetics (i.e. are cryptic) because rearranged segments are too small;
● May have no other molecular abnormalities, almost never > 50 chromosomes

Molecular images
=========================================================================



FISH: t(12;21)(p13;q22)



PreB ALL

B lymphoblastic leukemia / lymphoma with hyperdiploidy


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● “High hyperdiploidy” means >50 chromosomes and <66 chromosomes without translocations or other structural alternations
● Generally arises by simultaneous gain of all additional chromosomes in a single abnormal mitosis (Genes Chromosomes Cancer 2005;44:113)
● Hyperdiploidy appears to be an early event occurring prenatally (Genes Chromosomes Cancer 2004;40:38, Leukemia 2003;17:2202, Blood 2002;100:347)
● Affects 25-33% of children (usually age 3-5 years) and 5% of adults with B ALL; not seen in infants
● Favorable overall survival (Am J Hematol 2008;83:34), although outcome in children varies by specific trisomy present (Blood 2003;102:2756)
● Immunophenotype: CD19+, CD10-, CD34+ and CD45-

Micro description
=========================================================================

● No distinct morphology

Molecular description
=========================================================================

● Mutations in NRAS (10%), FLT3 (9%), PTPN11 (9%) and KRAS (6%, Genes Chromosomes Cancer 2008;47:26)
● Most common extra copies are 21, X, 14 and 4; least often 1, 2, 3
● Best prognosis of simultaneous trisomies: 4, 10 and 17



B ALL

B lymphoblastic leukemia / lymphoma with hypodiploidy


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Defined as fewer than 45 or 46 chromosomes
● 5% of B ALL
● 1% in both children and adults
● Most have 45 chromosomes, fewer chromosomes is rare

Prognostic features
=========================================================================

Poorer prognosis: near haploid and low hypodiploid groups compared to those with 42-45 chromosomes (Br J Haematol 2004;125:552), < 44 versus 44 chromosomes (Blood 2007;110:1112) and < 45 versus 45 chromosomes (Cancer 2003;98:2715)
● Poorest prognosis: near haploid 23-29 chromosomes, which appear limited to childhood
● Overall 50% survival at 8 years

Micro description
=========================================================================

● No distinct morphology

Molecular images
=========================================================================



Karyotype of severe hypodiploidy



Mature B cell ALL


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Also called Burkitt leukemia, FAB L3
● See also Lymphoma and plasma cell neoplasms chapter
● WHO classifies Burkitt lymphoma with secondary marrow or peripheral blood involvement and ALL-L3 as same disease
● Variants are endemic, sporadic and immunodeficiency associated, which have different clinical and geographic presentations
● Extramedullary masses are prominent, often the presenting feature
● Pure leukemic involvement is rare
● Cases with mature B phenotype but no c-myc translocations are best classified and managed as pre-B ALL (Arch Pathol Lab Med 2003;127:1340)

Case reports
=========================================================================

● 53 year old woman with hepatosplenomegaly (Arch Pathol Lab Med 2004;128:1459)

Treatment
=========================================================================

● More intensive chemotherapy than standard ALL plus CNS prophylaxis; overall survival up to 50-70% in adults (Blood 2004;104:3009)

Micro description
=========================================================================

● Intermediate to large blasts with intensely basophilic cytoplasm containing prominent vacuoles, nuclei are round with coarse / mildly clumped chromatin and indistinct nucleoli
● Low power has starry sky appearance in biopsies

Micro images
=========================================================================


             
Peripheral blood (fig 1A), bone marrow   Burkitt’s lymphoma
aspirate (fig 1B), bone marrow biopsy
(fig 2) and inset-CD20

Peripheral blood smears:
             
Large cells with prominent vacuoles

Bone marrow smears:
       
Large cells with basophilic cytoplasm and vacuoles

Stains:

Oil Red O+

Positive stains
=========================================================================

● CD10, CD19, CD20, CD22, CD79a, MUM1, PAX5, EBER
● Bright surface immunoglobulin with light chain restriction (overall is mature B cell phenotype)
● Oil Red O

Negative stains
=========================================================================

● CD5, CD23, CD34, TdT, BCL2



Other ALL

T cell acute lymphoblastic leukemia / lymphoma


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 20 March 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
=========================================================================

● Neoplasm of T lineage lymphoblasts which may form lymphomatous masses, involve blood and bone marrow (Stanford University)
● Also called pre T cell acute lymphocytic leukemia / lymphoma (preT ALL), T lymphoblastic leukemia / lymphoma (T LBL)
● See also Lymphoma and plasma cell neoplasms chapter
● Teens and young men (older than B ALL)
● Most cases begin after birth (Blood 2007;110:3036)
● T ALL versus T LBL: T ALL has more immature phenotype, CD47 expression, no 11q23 rearrangement (Pediatr Blood Cancer 2006;47:130), different gene expression profile and may derive from T cell progenitor of bone marrow; T LBL is derived from thymocytes (Leuk Lymphoma 2007;48:1745)
● T ALL constitutes 15% of childhood and 20-25% of adult ALL cases
● T LBL constitutes 85-95% of LBL, usually presents as mediastinal mass with no / minimal marrow involvement
● CNS involvement if untreated
● T LBL frequently presents with mass in anterior mediastinum, rapid growth, respiratory emergency, pleural effusion
● Younger (age 16-60 years) patients compared to older (61+ years) patients have more hepatosplenomegaly, present with mediastinal mass and lymphadenopathy; myeloid antigens and lineage inappropriate gene rearrangements are less common (Am J Clin Pathol 2002;117:252)
Diagnosis: T ALL if lymphoblasts are 25% or more of marrow cells; T LBL otherwise

Prognostic features
=========================================================================

Good prognostic factors: HOX11 overexpression in adults (Am J Clin Pathol 2007;127:528)
Poor prognostic factors: expression of CFLAR, NOTCH2 and BTG3 genes (Br J Haematol 2007;137:319), 3+ methylated genes (J Clin Oncol 2005;23:7043), residual disease after treatment (even if minimal)
● Pediatric patients with T ALL: TLX1(HOX11)+ was associated with favorable outcome, and TAL1+ and LYL1+ were associated with unfavorable outcome (Atlas of Genetics and Cytogenetics)
● Higher risk than B ALL due to presence of high risk features, but T ALL without high risk clinical features has survival comparable to B ALL

Treatment
=========================================================================

● Chemotherapy cures 60%
● Patients have earlier relapse, induction failure and isolated CNS relapse compared to preB ALL

Micro description
=========================================================================

● Similar to B cell disease; scant cytoplasm, delicate chromatin, indistinct nucleoli, convoluted nuclear membrane and grooves
● Frequent mitotic figures; starry sky pattern produced by interspersed benign macrophages
● Usually features of FAB L1 or L2; pattern in marrow is usually interstitial
● Lymph nodes: complete architectural effacement or partial involvement with paracortical infiltrate with germinal center sparing
● Thymus: replacement of normal parenchyma
● Occasionally eosinophilia and myeloid hyperplasia with variable t(8;13)(p11.2;q11-22) involving FGFR1 gene; some develop myeloid malignancy (MDS, AML, or myeloid sarcoma)

Micro images
=========================================================================



Blood smear shows atypical T cells


Blood smear shows markedly elevated leukocyte count with variable lymphoblast size and chromatin density

L2 type (blood smears):

Large leukemic blasts; also small cells with minimal cytoplasm, markedly hyperchromatic nuclei and prominent nuclear convolution, suggestive of T cell ALL

Bone marrow biopsy:

Sheets of lymphoblasts with variable size and moderate nuclear irregularity, also mitotic figures

Lymph node:

Axillary lymph node biopsy (figures a-c)

Stains:

Focal paranuclear acid phosphatase staining

Positive stains
=========================================================================

● CD1a, CD2 (78%), CD3 (cytoplasmic, not surface in 100%), CD5 (100%), CD7 (100%), TdT (73%)
● CD4 and CD8 both positive in 22%
● Variable CD10 (47%), CD13 (6%), CD16, CD33 (12%), CD56 (Haematologica 2009;94:160), CD57, CD79+ (40-60%, Am J Clin Pathol 2000;113:823), CD117 (12%, Exp Mol Pathol 2006;81:162)
● CD117 associated with activating mutations of FLT3, CD4 (10%) and CD8 (< 10%)

Negative stains
=========================================================================

● CD19, CD20; double negative CD4 / CD8 (40%)
Note: ALL with aberrant myeloid antigen expression is correct name, not biphenotypic leukemia

Molecular description
=========================================================================

● Different cytogenetic abnormalities than B ALL (Atlas of Genetics and Cytogenetics), often are cryptic and identified only by FISH or PCR
● t(1;14)(p32;q11) involving SCL (TAL1) and T cell receptor delta / alpha in 15-30%
● t(10;14)(q24;q11) involving HOX11 (TLX1) and T cell receptor delta / alpha in 7%
● Activating mutations of NOTCH1 in 50% (Science 2004;306:269)
● CDKN2A (INK4A) deletions in up to 80% (Blood 1995;85:2321)
● TCR: may have rearrangement, but is not lineage specific
● TCR loci (1/3 of T ALL):
     ● 14q11.2 (alpha, delta)
     ● 7q35 (beta)
     ● 7p(14-15) (gamma)

Genes:
● MYC (8q24.1)
● TAL1 (1p32)
● RBTN1 (LMO1) (11p15)
● RBTN2 (LMO2) (11p13)
● HOX11 (TLX1) (10q24)
● HOX11L2 (TLX3) (5q35)
● LYL1 (19p13)
● LCK (1p34.3-35)

Molecular images
=========================================================================



Chart of rearrangements involving T cell receptor genes


FISH: t(5;14)(q35;q32)

Differential diagnosis
=========================================================================

Burkitt leukemia: B cell phenotype
Granulocytic sarcoma: positive for myeloid markers
Mantle cell lymphoma-blastoid: B cell phenotype
Thymoma see Am J Clin Pathol 2004;121:268



Other ALL

Ambiguous Lineage


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 28 September 2012, last major update September 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Acute leukemias in which the morphologic, cytochemical and immuno-phenotypic features of the blasts:
      ● Lack sufficient evidence to classify as myeloid or lymphoid origin
      ● Or, have morphologic and/or immunophenotypic characteristics of both myeloid and lymphoid cells
      ● Or, have both B and T lineages (acute bilineal leukemia and acute biphenotypic leukemia)

Acute leukemias of ambiguous lineage include the following:
● Acute undifferentiated acute leukemia
● Mixed phenotype acute leukemia with t(9;22)(q34;q112.); BCR-ABL1
● Mixed phenotype acute leukemia with t(v;11q23); MLL rearranged
● Mixed phenotype acute leukemia, B/myeloid, NOS
● Mixed phenotype acute leukemia, T/myeloid, NOS
● Mixed phenotype acute leukemia, NOS rare types
● Other acute leukemias of ambiguous lineage

Epidemiology
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● <4% of all acute leukemias, more frequent in adults

Etiology
=========================================================================

● Unknown

Clinical features
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● Related to bone marrow failure: fatigue, infections, bleeding

Morphology
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● Acute undifferentiated leukemia
      ● Leukemic cells lack any differentiating features
● Acute biphenotypic and acute bilineal leukemias
      ● May present as one subtype of AML with features of ALL (B, T or B and T)

Immunophenotype
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Undifferentiated acute leukemia:
● Leukemias lack specific lineage markers
● cCD79a, cCD22, CD3 and MPO
● Generally don’t express more than one lineage-associated marker
● Often express HLA-DR, CD34, CD38, may express TdT and CD7

Bilineal acute leukemia
● Dual population of blasts, each with distinct lineage: positive for myeloid, lymphoid or B and T-cell markers (Leukemia 2007;21:2264)
● May evolve into biphenotypic acute leukemia (Atlas of Genetics and Cytogenetics)

Biphenotypic acute leukemia
● Blasts co-express myeloid and T or B lineage markers
● Or, concurrent B and T lineage markers
● Rarely co-express markers for myeloid, T and B lineages

● Co-expression of one or two cross-lineage (non specific) markers is not sufficient for biphenotypic leukemia; e.g. myeloid-antigen positive ALL or Lymphoid antigen-positive AML
● Lineage switch after therapeutic intervention
      ● Possible expansion of pre-existing minor population of blasts of different lineage following therapeutic suppression of the major population
      ● Possible lineage instability

Genetics
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● High degree of cytogenetic abnormalities
● 1/3 of cases have Ph chromosome
● t(4;11)(q21;q23) or 11q23, typically have CD10(–) precursor B lymphoid component
● T/myeloid biphenotypic or bilineal leukemia can have complex karyotypes

Cell of origin
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● Multipotent progenitor stem cell

Prognosis
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● Unfavorable, particularly in adults
● t(4;11) or Ph particularly unfavorable

Treatment
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● Usually aggressive chemotherapy or bone marrow transplant

Case reports
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● 5 year old boy with t(9;17)(p11;q11) (Leuk Lymphoma 1997;25:179)
● 20 year old woman with myeloid, B cell and NK phenotype (Arch Pathol Lab Med 2003;127:E93)
● 80 year old man with blasts coexpressing CD79a and myeloid markers (Arch Pathol Lab Med 2003;127:356)
● Due to transformation of essential thrombocythemia (Am J Hematol 2006;81:624)

Micro images
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Blood smears:

Child with t(4;11)(q21;q23) - small blasts are early B cell precursors that are CD10 negative,
large cells are monocyte precursors that are alpha naphthyl butyrate esterase+



Blasts have minimal cytoplasm, fine chromatin with 1+ prominent nucleoli


Bone marrow smears:

2 week old girl with t(4;11)(q21;q23) - lymphoblasts and monoblasts


2 week old girl with t(4;11)(q21;q23) - Large cells are monoblasts and promonocytes,
small cells are lymphoblasts with minimal cytoplasm and coarse chromatin



Myeloid features include Auer rod (fig 1A-asterisk) and myeloperoxidase staining (fig 1B)

Flow cytometry images
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Biphenotypic acute leukemia with CD19 and myeloperoxidase coexpression (figure B)

Electron microscopy images
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Monocytoid blast has folded nucleus and scattered small electron dense granules

Molecular / genetics description
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● Many cases have IgH and TCR rearrangements or deletions

Differential diagnosis
=========================================================================

● For biphenotypic acute leukemia
      ● Myeloid antigen positive ALL
      ● Lymphoid antigen positive AML
● For undifferentiated acute leukemia
      ● Minimally differentiated AML
      ● Unusual precursor-B-cell or T-cell ALL



Other ALL

Mixed phenotype acute leukemia (MPAL)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 28 September 2012, last major update September 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● De novo acute leukemia containing separate populations of blasts of more than one lineage (bilineal or bilineage), or a single population of blasts co-expressing antigens of more than one lineage (biphenotypic)

Excludes:
● Acute myeloid leukemia (AML) with recurrent translocations t(8;21), t(15;17) or inv(16)
● Leukemias with FGFR1 mutations
● Chronic myelogenous leukemia (CML) in blast crisis
● Myelodysplastic syndrome (MDS)-related AML and therapy-related AML, even if they have MPAL immunophenotype

Criteria for biphenotypic leukemia:
● Score of 2 or more for each of two separate lineages:


The European Group for the Immunological Classification of Leukemias (EGIL) scoring system



2008 WHO classification of acute leukemias of ambiguous lineage

Prognosis
=========================================================================

● Poor, overall survival of 18 months
● Young age, normal karyotype and ALL induction therapy are associated with favorable survival
● Ph+ is a predictor for poor prognosis
● Bone marrow transplantation should be considered in first remission


Major Categories

MPAL with t(9;22)(q34;q11.2); BCR-ABL1
=========================================================================

● 20% of all MPAL
● Blasts with t(9;22)(q34;q11.2) translocation or BCR-ABL1 rearrangement (Ph+) without history of CML
● Majority in adults
● High WBC counts

● Most of the cases B/myeloid phenotype
● Rare T/myeloid, B and T lineage, or trilineage leukemias

Morphology:
● Many cases show a dimorphic blast population, one resembling myeloblasts and the other lymphoblasts

Cytogenetic abnormalities:
● Conventional karyotyping for t(9;22), FISH or PCR for BCR-ABL1 translocation
● Additional complex karyotypes
● Ph+ is a poor prognostic factor for MPAL, with a reported median survival of 8 months
● Worse than patients of all other types of MPAL


MPAL with t(v;11q23); MLL rearranged
=========================================================================

● Meeting the diagnostic criteria for MPAL with blasts bearing a translocation involving the 11q23 breakpoint (MLL gene)
● MPAL with MLL rearranged rare
● More often seen in children and relatively common in infancy
● High WBC counts
● Poor prognosis
● Dimorphic blast population, with one resembling monoblasts and the other resembling lymphoblasts
● Lymphoblast population often shows a CD19+, CD10- B precursor immunophenotype, frequently CD15+
● Expression of other B markers usually weak
● Translocations involving MLL gene include t(4;11)(q21;q23), t(11;19)(q23;p13), and t(9;11)(p22;q23)
● Cases with chromosome 11q23 deletion should not be classified in this category

Cytogenetics images:


t(4;11)(q21;23) in bilineal leukemia


MPAL B/Myeloid, NOS
=========================================================================

● Meets the diagnostic criteria for MPAL with both B and myeloid lineages without Ph+ and MLL rearrangement
● B/myeloid acute leukemia accounts for 1% of all leukemias
● More common in adults, but also seen in children

Morphology:
● Dimorphic populations, resembling lymphoblasts and myeloblasts, or a single population resembling ALL

Genetics:
● Multiple different cytogenetic changes have been demonstrated, however none is proven to be specific in this subtype


MPAL T/Myeloid, NOS
=========================================================================

● Meets the diagnostic criteria for MPAL with both T and myeloid lineages without Ph+ and MLL rearrangement
● More often in children, though in adults as well
● Dimorphic populations, resembling lymphoblasts and myeloblasts, or a single population resembling ALL
● Other commonly expressed T-lineage markers include CD2, CD7
● Myeloid markers MPO, CD117, TdT, CD13 and CD33
● T cell plus myeloid cases may have 2p13 translocations or other unrelated anomalies (Leukemia 2007;21:2264)

End of Leukemia - Acute > Superpage


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