Leukemia-Acute
Last revised 11 December 2008
Last major update January 2008
Copyright (c) 2002-2008 PathologyOutlines.com, Inc.
Bold and underlined topics are hypertext links and may open a new window
Links in green are to free full text-no registration journals
Table of Contents for Leukemia-Acute chapter
Acute leukemia: general
AML: general, classification
AML recurrent genetic abnormalities: t(8;21), inv(16) or t(16;16), APL with t(15;17), APL with t(V;17), APL-therapy related, 11q23 abnormalities, FLT3 mutations, t(6;9), multilineage dysplasia, therapy related
AML not otherwise categorized: minimally differentiated, without maturation, with maturation, M3, myelomonocytic, monoblastic and monocytic, erythroid, megakaryoblastic, CD13/CD33 negative, basophilic, myeloid sarcoma, acute panmyelosis with myelofibrosis, with Philadelphia chromosome, with pseudo Chediak-Higashi anomaly, hypocellular
ALL: general, WHO classification, with eosinophilia
PreB ALL: general, t(9;22), t(v;11q23), t(1;19), t(12;21), hyperdiploidy, hypodiploidy, mature B cell ALL/Burkitt’s
Other ALL: preT, bilineal, biphenotypic
See also Chronic leukemia topics in other chapters:
B cell leukemias: chronic lymphocytic, hairy cell, preB lymphoblastic, prolymphocytic leukemia, leukemic phase of mantle cell lymphoma
T/NK cell leukemias: NK cell, adult T cell, preT lymphoblastic, T cell large granular, T cell prolymphocytic, Sezary syndrome
Myelodysplastia / myeloproliferative disorders: chronic myelomonocytic (CMML), juvenile myelomonocytic, chronic myeloid (CML), chronic neutrophilic, chronic eosinophilic
Bone chapter: plasma cell leukemia
Primary references for Leukemia-Acute chapter
American Journal of Clinical Pathology (AJCP) [free full text and no registration after 1 year]; January 1997 to January 2008
American Journal of Surgical Pathology (AJSP); August 1979 to January 2008
Archives of Pathology and Laboratory Medicine (Archives) [always free full text and no registration]; January 1997 to December 2007
Biomed Central [always free full text and no registration]; 1 March 1997 to 3 January 2008
Human Pathology (Hum Path); January 1997 to January 2008
Modern Pathology (Mod Path) [free full text and no registration after 1 year]; January 1988 to January 2008
Rosai, J: Ackerman’s Surgical Pathology (9th Ed), Mosby, 2004
Sternberg, S: Diagnostic Surgical Pathology (4th Ed); Lippincott Williams & Wilkins, 2004
Brunning: Tumors of the Bone Marrow (AFIP Atlas of Tumor Pathology, Series 3, Vol 9, 1994)
Websites (images): ASH image bank
Journal search terms: “leukemia” and each topic below
Please refer to these primary references for more detailed discussions and photographs
Acute leukemia
“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
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 important to assess cellularity and 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
Common myeloid immunostains: CD13, CD14, CD15, CD33, CD36, CD61, CD64
Micro: bone marrow usually markedly hypercellular with replacement of normal cells; myelofibrosis relatively common; marrow is rarely hypocellular resembling aplastic anemia, but most cells are blasts
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 be granulomas associated with microorganisms
AML
Acute myeloid leukemia (AML) - general
Also called acute myelogenous leukemia
Neoplastic proliferation of hematopoietic precursor cells, causing excessive myeloblasts and other immature myeloid cells
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 leukemia but only 20% of childhood leukemia
Neoplastic blasts have normal proliferation rates but reduced maturation rates compared to normal blasts
Risk factors: most patients have none; Down’s syndrome, Bloom’s syndrome, Fanconi’s anemia, neurofibromatosis, benzene exposure, radiation, alkylating agents, type II topoisomerase inhibitors
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, > 100,000 in 20%; due to circulating blasts and other immature myeloid cells; in aleukemic leukemia, peripheral blood lacks blasts, and must examine bone marrow
Favorable prognostic factors: young patients, rapid response to chemotherapy, see favorable cytogenetics 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)
Diagnosis: examination of blood, marrow smears and cytochemical stains is usually sufficient; immunostains may be required for poorly differentiated leukemia
Peripheral smear: anisopoikilocytosis (variation in size and shape of red blood cells), nucleated red cells, neutropenia, thrombocytopenia, hypogranular and hyposegmented neutrophils, large atypical platelets
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
Acute myeloid leukemia (AML) - general - continued
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; see descriptions of various 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: type I myeloblasts #1; #2; type II myeloblasts; type III myeloblasts #1; #2
Micro images: two myeloblasts each have a single prominent Auer rod; Auer rod in neutrophil
Cytogenetics: 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)
Intermediate cytogenetics: t(15;17)(q22;q12), +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
Enzyme cytochemistry: positive for myeloperoxidase (Mod Path 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
Positive stains: myeloid markers (CD13, CD14, CD15, CD33, CD36), CD99 (43% of AML, 55% of chloromas, Mod Path 2000;13:452); often expresses B cell antigens CD20, CD7, PAX5, OCT2 or BOB.1 (AJCP 2006;126:916); VEGF expression varies by subtype (AJCP 2003;119:663)
Negative stains: CD10
Immunohistochemistry compared with flow cytometry: CD34 has similar findings, CD15 and CD117 are more sensitive by flow, myeloperoxidase is more sensitive by immunohistochemistry (Archives 2001;125:1063)
DD: reactive process (growth factor treatment causes increased blasts), transient myeloproliferative disorder of newborns resembles AML-M7, ALL, myelodysplastic syndrome
Sources for testing (advertisements): Genzyme (Flow cytometry), Genzyme (FISH)
References: eMedicine, Wikipedia, US National Cancer Institute
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) requires only 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) (AML1/ETO)
- AML with inv(16)(p13q22) or t(16;16)(p13;q22) (CBFβ/MYH11)
- Acute promyelocytic leukemia (AML with t(15;17)(q22;q12) (PML/RARα) and variants
- AML with 11q23 (MLL) abnormalities
Acute myeloid leukemia with multilineage dysplasia
Acute myeloid leukemia and myelodysplastic syndrome, therapy related
- Alkylating agent related
- Topoisomerase II inhibitor related
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 and M5b)
- Acute erythroid leukemia (M6)
- Acute megakaryoblastic leukemia (M7)
- Acute basophilic leukemia
- Acute panmyelosis with myelofibrosis
- Myeloid sarcoma
Acute leukemia of ambiguous lineage
- Undifferentiated acute leukemia
- Bilineal acute leukemia
- Biphenotypic acute leukemia
AML with recurrent genetic
abnormalities
Also called AML1-ETO leukemia
Translocation produces fusion product of ETO gene on #8q22 and AML1 gene on #21q22
5-10% of AML, 33% of cases of AML-M2 (AML with maturation); most common type of childhood AML
AML1-ETO may facilitate accumulation of genetic alterations by suppressing endogenous DNA repair (Blood 2007 Nov 1 [Epub ahead of print])
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)
Favorable prognosis in adults, although KIT activating mutations confer poorer prognosis
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 (AJCP 2006;125:267)
Case reports: with occult mastocytosis (J Clin Pathol 2004;57:324)
Micro: 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 (AJCP 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; various images #1; #2-H&E and stains
Positive stains: CD19 (75-93%) and CD56 (82%) (aberrant expression compared to classic AML M2, AJCP 2007;128:550); also PAX5/BSAP (usually weak) and Oct2 (75%, AJCP 2006;126:235); high levels of CD34 and myeloperoxidase and low levels of CD33 by flow cytometry (Mod Path 2004;17:1211)
Negative stains: CD20, CD22, CD79a
Molecular: AML1 gene also called RUNX1, encodes core binding factor alpha
Cytogenetic images: t(8;21) with abnormal chromosomes on right, and breakpoints at arrowheads; various images; variants
AML with inv(16)(p13;q22) or t(16;16)(p13;q22)
Also called M4Eo
8% of adult AML, 25% of acute myelomonocytic leukemia (AML M4) cases
Associated with more frequent hepatosplenomegaly, lymphadenopathy and granulocytic sarcoma than AML in general
Longer median survival than other AML (AJCP 2003;119:672); complete remission rates are 76% to 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)
Poorer prognostic factors are high initial WBC count for complete response and age > 35 years for disease free survival (Blood 2003;102:462)
Peripheral blood: monocytosis, high blast counts
Micro: usually AML M4 (acute myelomonocytic leukemia) features plus marrow eosinophilia with dysplastic eosinophils containing large basophilic staining granules in addition to usual eosinophilic granules; usually >10% dysplastic forms in at least one lineage (AJCP 2003;120:236)
Micro images:
bone marrow smears (Wright-Giemsa): eosinophil precursors show prominent basophilic staining granules #1; #2; H&E, cytogenetics and FISH; immature cells with folded, monocytoid nuclei mixed with abnormal eosinophils (arrow) containing large basophilic granules and more normal eosinophil granules; various eosinophil precursors; various images #1; #2; #3; #4; #5 (some images associated with cytogenetic changes); H&E, RT-PCR and FISH
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, AJSP 2006;30:1436)
Molecular: inversion(16) or t(16;16)(p13;q22) are due to breaks in smooth muscle myosin heavy chain gene (SMMHC) producing MYH11 at 16p13 and core binding factor beta (CBF-beta) gene at 16q22, creating CBF-beta - MYH11 protein (Science 1993;261:1041, Proc Natl Acad Sci USA 1998;95:11863); multiple fusion transcripts exist (J Mol Diagn 2004;6:22); fusion transcripts appear to upregulate NF-kappaB signaling pathway (Mod Path 2007;20:811)
Molecular images: two G banded chromosome 16 pairs show pericentric inversion at #16, arrowheads point to breakpoints on abnormal chromosome; diagram; karyotype
Acute promyelocytic leukemia (APL) with t(15;17)(q22;q12)
Either hypergranular (this section) or microgranular (section below)
8% of AML cases, 15% of adult AML
Formerly called AML M3
Median age 35-40 years
Decreased WBC count at presentation with abnormal promyelocytes; usually severe disseminated intravascular coagulation (DIC) and hemorrhage before or during induction chemotherapy, which may cause early death; organomegaly or extramedullary disease is unusual
Rarely has skin involvement, detected with FISH (Mod Path 2005;18:1569)
Criteria for diagnosis: most cells (>50%) are abnormal promyelocytes with heavy cytoplasmic granulation, often reniform nucleus; cells with multiple Auer bodies usually present
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)
Case reports: 45 year old man with fatigue
Treatment: (1) all trans retinoic acid (ATRA) causes neoplastic promyelocytes to rapidly differentiate into bizarre maturing neutrophils, but patients eventually relapse; (2) arsenic trioxide (ATO) for ATRA-refractory patients; induces differentiation at low doses, marrow necrosis at high doses (Mod Path 2000;13:954); (3) combination chemotherapy required for sustained remissions (Hematology Am Soc Hematol Educ Program 2006;147)
Survival: excellent if DIC and hemorrhage are adequately controlled; excellent in adults with complete remission
Micro: most cells are hypergranular promyelocytes (abundant cytoplasm, round/oval and frequently eccentric nuclei with occasional clefts or indentations, moderately condensed chromatin, indistinct nucleoli) with heavy red/purple cytoplasmic granulation that may obscure nuclear borders; 90% have multiple Auer rods in some cells, which may be intertwined (“faggot” cell-word is derived from Middle English/Old French term for bundle of twigs, sticks, or branches bound together); 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)
Acute promyelocytic leukemia (APL) with t(15;17)(q22;q12) - continued
Micro images:
bone marrow smears (Wright-Giemsa): abundant azurophilic granules #1, also two microgranular promyelocytes with basophilic cytoplasm and lobulated nuclei; #2; numerous Auer rods in bundles
bone marrow biopsy: bone marrow is almost completely replaced by promyelocytes with abundant cytoplasm, oval/round nuclei that are often eccentrically located, with occasional indentations/clefts, somewhat condensed chromatin and indistinct nucleoli; promyelocytes are relatively uniform with abundant cytoplasm containing dense azurophilic granules and multiple Auer rods, nuclei are round, oval and lobulated
treatment related: before and after arsenic trioxide; post-chemotherapy smear shows single “faggot” cell with numerous Auer rods in bundles
other sites: skin infiltration-various H&E and FISH
stains: CD99 (figures 3C/3D); H&E and CD99 (fig A1/A2)
Positive stains: CD9, CD11a, CD11b (post-treatment only-ATRA: Archives 2003;127:e4 or arsenic trioxide: Mod Path 2000;13:954), CD13, CD33, CD79a (86% but varies by clone, AJCP 2007;128:306), myeloperoxidase (strong), CD2 (23%), CD64 (27%), HLA-DR (9%); variable CD34, CD71, CD99
Negative stains: CD11b (but post-treatment is positive), CD11c (AJCP 1998;109:211), CD14, CD34, CD36, CD41, CD61, glycophorin A
Molecular: t(15;17) translocation not found in other AML subtypes; breakpoints at PML gene on #15q22 and retinoic acid receptor alpha (RARa) 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) (AJCP 1999;112:113)
Cytogenetic images: t(15;17)-arrowheads at breakpoints on abnormal chromosomes; karyotype
Molecular images: FISH - negative and positive control of t(15;17)
EM: Auer rods have tubular substructure, markedly dilated endoplasmic reticulum, stellate complexes of rough ER, nucleus has dispersed chromatin and prominent nucleolus
EM images: cytoplasm has numerous dense granules and several Auer rods, nucleus has dispersed chromatin and prominent nucleolus; cross section of Auer rod shows characteristic tubular structure
References: Atlas of Genetics and Cytogenetics
Microgranular variant of acute promyelocytic leukemia
Formerly called AML-M3v
Note: “variant” APL without further description may mean microgranular variant or cytogenetic variant (see below)
Peripheral blood white blood count usually elevated, in contrast to hypergranular form
Diagnosis: cytogenetics recommended, because other AML cases may appear similar (AJCP 2002;117:651)
Case reports: 5 year old girl with Down’s syndrome (J Med Case Reports 2007;1:147), post-chemotherapy with atypical breakpoints for translocation (Cancer Genet Cytogenet 2002;138:143), occuring after untreated essential thrombocythemia (Am J Hematol 2002;71:114)
Micro: leukemic cells have fewer and smaller cytoplasmic granules, usually multiple Auer rods but less than classic (hypergranular) promyelocytic leukemia; nuclei is folded, convoluted, markedly irregular
Micro images: promyelocytes have abundant fine, azurophilic cytoplasm with variable size and basophilia, markedly lobulated and invaginated nuclei #1; #2; small hyperbasophilic promyelocytes with prominent cytoplasmic budding, most cells have sparsely granular cytoplasm and lobulated nuclei #1; #2
Positive stains: CD34 (more common than hypergranular variant, Haematologica 2006;91:311), CD13, CD33, myeloperoxidase (strong), usually CD2 (Leukemia 1995;9:1461)
Molecular: associated with FLT-3 aberrations (Br J Haematol 2004;125:463) and different gene expression profile than hypergranular APL (Genes Chromosomes Cancer 2005;43:113)
EM: stellate array of endoplasmic reticulum is characteristic
EM images: smaller granules than hypergranular variant, granules are more uniform in size, endoplasmic reticulum is prominent; small granules and stellate array of endoplasmic reticulum
DD: other AML (AJCP 2002;117:651)
References: Blood 1980;55:253
Acute promyelocytic leukemia with t(V;17)(V;q12)
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
DIC common; may NOT respond to all-trans retinoic acid; may be more aggressive than classic acute promyelocytic leukemia (Blood 1995;85:1083)
Recommended to combine cytogenetics, FISH and molecular biology to document presence / absence of PML-RARalpha fusion gene in complex cases (Cancer Genet Cytogenet 2005;159:69)
Case reports: with PRKAR1A gene (Blood 2007;110:4073), t(17;20) masking t(15;17) (Cancer Genet Cytogenet 2006;168:73)
Micro: features are intermediate between hypergranular acute promyelocytic leukemia (M3) and acute leukemia with maturation (M2) - most cells have many granules, usually no Auer rods, regular nuclei but increased pseudo Pelger-Huet cells
Micro images: cells with many granules, no Auer rods, regular nuclei
Molecular: involves RAR alpha and either PLZF (11q23), NUMA (11q13), NPM (5q31) or STAT5b genes (Leukemia 2002;16:1927)
DD: t(11;17) may resemble AML with 11q23 abnormality (Cancer Genet Cytogenet 2005;159:168)
References: Atlas of Genetics and Cytogenetics-t(11;17)
Acute promyelocytic leukemia-therapy related
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
Mitoxantrone and etoposide or its metabolites stimulate topoisomerase II to cleave different sites in PML and RARA (N Engl J Med 2005;352:1529)
Case reports: microgranular variant developing post-chemotherapy for breast cancer (Cancer Genet Cytogenet 2002;138:143), post-radioactive iodine for thyroid cancer (J BUON 2007;12:129), developing post-chemotherapy in 8 year old girl with non Hodgkin’s lymphoma (J Pediatr Hematol Oncol 2004;26:427)
Micro: classic findings of APL plus dyserythropoiesis and dysmegakaryopoiesis
Molecular: t(15;17)(q22;q12), often with additional abnormalities; PML-RARa in most cases; FLT-3 gene mutations in 42%
References: AJCP 2005;123:840
AML with 11q23 (MLL) abnormalities
3-5% of AML (Anticancer Res 2005;25:1931)
Usually children or young adults
Present in high percentage of topo II inhibitor, therapy related AML (Blood 2003;102:2395); also ALL and biphenotypic leukemia
More than 50 chromosomal loci have been identified as 11q23 partners, but most common are t(9;11)(p21;q23) [AF9-MLL] and t(4;11) [AF4-MLL]
FISH is more sensitive than conventional cytogenetics in detecting MLL; may also detect 11q22-25 rearrangements that are MLL negative (AJCP 2004;122:298)
PCR is more sensitive than conventional cytogenetics in detecting MLL/ENL [t(11;19)] fusion transcripts (AJCP 2007;127:24)
Typically poor prognosis
MLL partial tandem duplication: present in 93% of normal cord blood samples at low levels (Leuk Res 2006;30:1091); associated with normal karyotype or trisomy 11; typically poor prognosis in AML (Br J Haematol 2006;135:438), but recent study showed similar outcome (Blood 2007;109:5164)
Micro: blasts resemble monoblasts, monocytes or myelomonocytes (AML M4, M5)
Positive stains: nonspecific esterase
Molecular: involves MLL-mixed lineage or myeloid/lymphoid leukemia gene, present in both AML and ALL; is also called HTRX1, HRX and ALL1; translocations occur in AML (intermediate prognosis) and ALL (poor prognosis, Blood Cells Mol Dis 2007 Sep 28 [Epub ahead of print])
Molecular images: partner genes; diagram of MLL/ALL1 duplication
Cytogenetics images: t(4;11)(q21;23) in bilineal leukemia
References: OMIM 159555, Atlas of Genetics and Cytogenetics
Not a WHO diagnosis
Mutations of FMS-like tyrosine kinase 3 (FLT3) occur in 20-30% of de novo AML
Most frequent molecular abnormality in AML
Usually peripheral leukocytosis and normal cytogenetics
Mutations include internal tandem duplication/juxtamembrane domain (ITD) and tyrosine kinase domain (TKD)
FLT3-ITD associated with poor prognosis (Blood 2002;100:1532), FLT3-TKD doesn’t affect prognosis (Blood 2007 Oct 26 [Epub ahead of print])
Diagrams: FLT3 structure
Micro: monocytic differentiation
Molecular: usually normal cytogenetics; most common mutation is internal tandem duplication mutation (ITD)
Molecular images: activating ITD mutations (diagram)
Not a WHO diagnosis
1% of AML
Usually women, median age 51 years, range 20-76 years
Often DIC, basophilia
Poor prognosis
Treatment: allogeneic hematopoietic stem cell transplantation; monitor by real time RQ-PCR (Leukemia 2005;19:1338)
Micro: intermediate features between AML with maturation (AML M2), acute promyelocytic leukemia and acute myelomonocytic leukemia; often ringed sideroblasts (AJCP 1997;107:430)
Positive stains: CD9, CD13, CD33, CD34 (92%), CD38, CD117, HLA-DR, TdT (64%)
Molecular: produces DEK-CAN fusion protein; 88% have FLT3 gene mutations, often additional chromosomal abnormalities
Cytogenetic images: karyotype #1; #2; karyotype-bottom row
References: AJCP 2004;122:348, Atlas of Genetics and Cytogenetics
AML with multilineage dysplasia
Arises either as de novo AML or from existing myelodysplastic syndrome
Includes what was previously called refractory anemia with excess blasts in transformation
Usually presents with severe pancytopenia
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
Prognosis: controversial - poorer (AJCP 2003;119:672) versus no independent prognostic value (Blood 2007 Dec 4 [Epub ahead of print]) versus poor only with adverse cytogenetics (Eur J Haematol 2002;68:203)
Micro: dysplasia in 50% of cells of 2 or more lineages; often panmyelosis, usually dysplastic megakaryocytes
Micro images: prior MDS - various images #1; #2
no prior MDS - various images #1; #2; #3; #4; #5; #6
Positive stains: CD34, CD117, HLA-DR
Molecular: trisomy 8, abnormalities of #5 or #7 are common; also t(3;5)(q25;q34-35) involving MLF1 and NPM (Hum Path 2003;34:809)
DD: acute erythroid leukemia, AML M2, AML M6a
AML and myelodysplastic syndrome - therapy related
May occur post-chemotherapy or post-radiation therapy
Rarely occurs after therapy for de novo AML (Leuk Res 2007 Dec 17 [Epub ahead of print))
Includes therapy related myelodysplastic syndrome, which has close relationship to therapy related AML
Similar genetic abnormalities as de novo myelodysplasia and AML, although 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 is children and adults may actually be similar (J Toxicol Environ Health B Crit Rev 2007;10:379)
References: Haematologica 2007;92:1389
Alkylating agents as cause of therapy related AML and myelodysplastic syndrome
Occurs median 5 years after initiation
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
Poor prognosis; median survival is 7-8 months
Micro: hypocellular marrow; often severe dysplastic changes in blood and marrow; myelofibrosis and ringed sideroblasts common; <5% myeloblasts
Molecular: abnormalities of chromosomes 5 or 7 or complex cytogenetic abnormalities
Topoisomerase II inhibitors as cause of therapy related AML and myelodysplastic syndrome
Occurs mean 2-3 years after initiation of etoposide or teniposide with doxorubicin
Usually presents as acute monocytic or myelomonocytic leukemia
Poor prognosis
Molecular: 11q23 and 21q22 abnormalities
Other agents as cause of therapy related AML and myelodysplastic syndrome
Case reports: t(4;11) post-rituximab and fludarabine for SLL (Cancer Genet Cytogenet 2007;177:143)
AML not otherwise categorized
Acute myeloblastic leukemia, minimally differentiated (M0)
5% of AML cases
Typically presents with thrombocytopenia, neutropenia and marrow failure
No definitive evidence of myeloid differentiation by morphology and cytochemistry; need immunohistochemistry or EM to characterize as myeloid
Criteria for diagnosis: nongranular blasts; less than 3% of blasts are positive for myeloperoxidase or Sudan Black B 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
Children (Blood 2007;109:2314) and adults (Br J Haematol 2001;113:737) may have poorer outcome than other AML subtypes
Micro: nongranular, medium sized-blasts, no Auer rods, dispersed chromatin; small blasts may resemble lymphoblasts
Micro images:
bone marrow smear (Wright-Giemsa): no differentiated features #1; #2
bone marrow biopsy: complete replacement of marrow by blasts without differentiation
stains: myeloblasts are negative for myeloperoxidase by cytochemistry with positive staining in neutrophil; blasts are positive for myeloperoxidase by IHC; CD99
Enzyme cytochemistry: negative for myeloperoxidase, Sudan Black B, chloroacetate esterase, nonspecific esterase
Positive stains: CD13, CD33 (AJCP 2001;115:876), CD34, CD117 (AJCP 2002;117:380), HLA-DR, CD38; variable expression of myeloperoxidase, Sudan Black B, TdT, CD2, CD4, CD7 and CD71
Negative stains: CD14 (usually), CD36 (usually), CD41, CD61, CD64 (usually, Archives 2007;131:748), most lymphocyte antigens; glycophorin A
Flow cytometry: pediatric AML-M0 is usually CD33 bright, TdT-, CD34-, CD13-/weak (AJCP 2000;113:193)
EM: resembles myeloblasts; may show focal myeloperoxidase+ granules
EM images: granules are myeloperoxidase positive #1; #2
Molecular: often complex chromosomal abnormalities; 31% have AML1/RUNX1/core binding factor alpha mutation, associated with trisomy 13 and FLT3 mutation (Haematologica 2007;92:1123); tend to have more 5-, trisomy 21 and hypodiploidy than other AML, although outcome is similar (Blood 2007;109:2314)
DD: ALL, M7, biphenotypic leukemia
Acute myeloblastic leukemia without maturation (M1)
10-20% of AML cases, 44% in one Brazil hospital (Sao Paulo Med J 2006;124:45)
4% of childhood AML (Orphanet)
Usually adults presenting with anemia, thrombocytopenia and neutropenia
Criteria for diagnosis: at least 90% of nonerythroid cells in marrow are myeloblasts; if no Auer rods, at least 3% of blasts must be positive for myeloperoxidase or Sudan Black B by enzyme cytochemistry
Case reports: large and small blasts (Archives 2004;128:448), presenting with arterial thromboembolism (Leuk Res 2007;31:869); t(6;9) and basophilia (Ann Biol Clin (Paris) 2003;61:352)
Micro: very immature cells, usually round with few cytoplasmic granules or Auer rods; nuclei are round or indented; little maturation beyond myeloblast stage; cells may not appear myeloid cytologically; typically markedly hypercellular marrow
Micro images:
bone marrow smears (Wright-Giemsa): blasts show mild size variation, have pale to slightly basophilic agranular cytoplasm, uniform nuclei with fine chromatin and prominent nucleoli; blasts show more variation in size and number of nucleoli, four blasts have Auer rods; myeloblasts have irregular nuclei with folding and invagination, one myeloblast has numerous azurophilic granules; myeloblasts have marked size variation, irregular nuclei with condensed chromatin, no nucleoli, one blast has a thin Auer rod; some variation in size, two myeloblasts have more intense basophilic cytoplasm and coarse nuclear chromatin; myeloblasts are large with abundant eosinophilic cytoplasm, two cells have prominent Auer rods, one cell has numerous azurophilic granules, 2 post-mitotic erythroblasts are also present; agranular myeloblasts have variation in size, cytoplasmic volume and cytoplasmic basophilia; various images #1; #2
bone marrow biopsy: marrow is completely replaced by blasts with variable cytoplasm, round/oval nuclei with mild irregularities and small/indistinct nucleoli; biphasic morphology (large and small blasts)
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)
Acute myeloblastic leukemia without maturation (M1) - continued
Enzyme cytochemistry: at least 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
Positive stains: at least two myelomonocytic antigens (CD13, CD33, CD117); CD34, CD99 (Mod Path 2000;13;452); variable CD15, CD71 and HLA-DR
Negative stains: CD14 (usually), CD36 (usually), CD41, CD61, CD64 (usually), glycophorin A
EM: may have heterogeneous features (Ultrastruct Pathol 1995;19:9)
Molecular: 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)
DD: ALL, AML-M0, AML-M2
Acute myeloblastic leukemia with maturation (M2)
30-45% of AML cases; 5% of childhood leukemias (Orphanet)
Any age, 20% are < 25 years and 40% are 60 years+
Variable prognosis
Criteria for diagnosis: 20%+ nonerythroid cells in peripheral blood or bone marrow are myeloblasts; monocytic precursors are < 20%, granulocytes are >10% of cells
Case reports: with t(5;11) (Cancer Genet Cytogenet 2007;172:154)
Micro: usually hypercellular marrow; full range of myeloid maturation through maturing neutrophils, often with abnormal segmentation; Auer rods in 70% of blasts; variable azurophilic granules; erythroid and megakaryocyte precursors may have dysplastic changes; often increased eosinophil precursors; 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, also several erythroblasts; several blasts have prominent nucleoli and Auer rods, also a promyelocyte and myelocyte; several myeloblasts and maturing forms, also neutrophils with agranular cytoplasm; large myeloblasts have pseudopods, usually abundant cytoplasm, some with prominent Auer rods; various images #1; #2; #3; #4; #5; #6; #7; #8; promyelocytes
bone marrow biopsy: markedly hypercellular marrow has predominantly blasts, also scattered erythroid precursors and eosinophils
stains: myeloperoxidase+ blasts, neutrophils are intensely positive; myeloperoxidase+ blasts and immature neutrophils, erythroid cells are negative; Sudan black B+ and chloroacetate esterase+
diagnosed as AML with maturation because no t(15;17) and no DIC, but FISH not done, so may actually be acute promyelocytic leukemia: abundant coarse azurophilic granules #1; #2 with specific granules resembling Chediak-Higashi anomaly; #3 with numerous promonocytes
Enzyme cytochemistry: most blasts are positive for myeloperoxidase or Sudan Black B, and chloroacetate esterase
Positive stains: CD13, CD33, CD34, HLA-DR, CD71 (variable), CD99
Negative stains: CD14 (usually), CD36 (usually), CD41, CD61, CD64 (usually), glycophorin A
EM images: numerous primary granules and fusion of Auer rods
Molecular: associated with t(8;21) (Cytometry B Clin Cytom 2008;74:25); FLT3 mutations associated with HLA-DR negative patients (Leuk Res 2007;31:921)
DD: leukemoid reaction, AML with multilineage dysplasia, refractory anemia with excess blasts, AML-M1, M3, M4
Acute promyelocytic leukemia (M3)
See Acute promyelocytic leukemia with t(15;17)(q22;q12)
Acute myelomonocytic leukemia (M4)
See also AML with inv(16)(p13;q22) or t(16;16)(p13;q22)-M4eo
15-25% of AML cases, 3% of childhood leukemia (Orphanet)
Children and adults
Often markedly elevated WBC with anemia and thrombocytopenia, organomegaly, lymphadenopathy and other tissue infiltration (monocytes infiltrate)
May occur post-therapy (myeloma-Sichuan Da Xue Xue Bao Yi Xue Ban 2007;38:347)
Criteria for diagnosis: myeloblasts, monoblasts and promonocytes are 20% or more of nonerythroid cells; myeloblasts and granulocytes are 80% or less of nonerythroid 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 5000/mm3 or more
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
Case reports: leukemic ascites (Archives 2005;129:262), pregnant woman (Internet J of Hematology 2003; Vol 1, No. 1), 30 year old woman with gingival hyperplasia, catastrophic antiphospholipid antibody syndrome (J Pediatr Hematol Oncol 2004;26:327)
Micro: myelocytic and monocytic differentiation evident; myeloid cells resemble M2 (60% of myeloblasts have Auer rods) but at least 20% of nonerythroid cells are large, monocyte lineage cells with abundant pale gray-blue cytoplasm and prominent nucleoli; promonocytes have abundant cytoplasm containing fine azurophilic granules and delicately folded nuclei
Micro images:
bone marrow smears (Wright-Giemsa): mixture of monocytes and neutrophils at different stages of maturation, also several promonocytes with abundant cytoplasm containing fine azurophilic granules and delicately folded nuclei; promonocytes on left have basophilic cytoplasm with coarse azurophilic granules, those in upper right have abundant pale cytoplasm with delicate nuclear folds; three promonocytes have abundant cytoplasm with fine azurophilic granules, also dysplastic neutrophil with pseudo-Pelger-Huet nucleus in upper left; five promonocytes and two myelocytes (center), one containing numerous azurophilic granules and an Auer rod; various images #1; #2
Acute myelomonocytic leukemia (M4) - continued
bone marrow biopsy: markedly hypercellular marrow with heterogeneous cells, including immature monocytes (irregular nuclei and prominent nucleoli) and neutrophils; resembling sarcomatoid carcinoma
other sites: leukemic ascites
stains: chloroacetate esterase stains neutrophils blue, and nonspecific esterase stains monocytes red-brown; non-specific esterase; CD68; lysozyme; peroxidase (myeloid marker)
Enzyme cytochemistry: monoblasts are positive for nonspecific esterase; if negative, confirm monocyte lineage with immunohistochemistry or EM
Positive stains: may vary between monocyte and myeloid populations; CD4, CD11, CD13, CD14 (possibly), CD33, CD36, CD64, CD68, CD71 (variable), HLA-DR, lysozyme, myeloperoxidase; variable CD56, CD34, CD117 (AJCP 2004;122:865)
Negative stains: CD41, CD61, glycophorin A, keratin
Molecular: may have recurrent genetic abnormalities of inv(16) or 11q23 rearrangement
DD: leukemoid reaction, G-CSF related transient atypical monocytosis (Clin Lab Haematol 2004;26:359), myelodysplastic syndrome, AML M2, M5, microgranular M3, sarcomatoid carcinoma
Acute monoblastic and acute monocytic leukemia (M5)
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 and M5b have similar immunophenotype, cytogenetics and clinical outcome (Leuk Res 2007 Aug 7 [Epub ahead of print]), although M5a may have higher expression of CD68 and CD11c (Zhongguo Shi Yan Xue Ye Xue Za Zhi 2006;14:1079); but see Zhongguo Shi Yan Xue Ye Xue Za Zhi 2006;14:654 (cytogenetics are different)
Similar prognosis as other subtypes (J Clin Oncol 2004;22:1276)
Criteria for diagnosis: 80% or more nonerythroid bone marrow cells are monocyte lineage
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: CD11b (80-90%, AJCP 1997;107:283), CD11c (50%), CD13, CD33, CD64 (AJCP 1998;110:797), CD68, HLA-DR
Cytogenetics: 11q23 translocations in 19%, trisomy 8 in 17%
References: Orphanet
Acute monoblastic leukemia (M5a)
5-8% of AML
Children and young adults
Criteria for diagnosis: 80% or more monocyte lineage cells are monoblasts
Case reports: with mantle cell lymphoma (Leuk Lymphoma 2005;46:1813), erythropoietin-dependent transformation of refractory anemia with ringed sideroblasts into acute monoblastic leukemia (Blood 2001;98:3492)
Micro: hypercellular marrow with large number of monoblasts; monoblasts are large with moderately abundant cytoplasm, variably basophilic and delicate azurophilic granules but no/rare Auer rods; may have pseudopods or vacuoles; have round nuclei with prominent nucleoli but no folds; promonocytes have abundant cytoplasm with fine 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 has 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 #1; #2-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; t(8;16) with erythrophagocytosis; bone marrow and skin; various images #1; #2
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 #1; #2 (fig 4), case also has neoplastic plasma cells; monoblasts are positive for CD68 #1 (KP-1); #2; buffy coat smear-vacuoles are PAS+
Positive stains: CD13, CD14 (most), CD68, PAS (vacuoles), nonspecific esterase (strong), lysozyme
Negative stains: myeloperoxidase
EM 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
Molecular: 75% have cytogenetics abnormalities, including 11q23 in 30% (these cases should be classified as a recurrent genetic abnormality); FLT3 mutations in 7%
DD: ALL-L2, AML-M0, M1, M7
Acute monocytic leukemia (M5b)
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 (Archives 1999;123:1111)
Case reports: cutaneous disease (Archives 2005;129:425), with coexisting myeloma (Archives 2003;127:1506), 60 year old woman with fatigue, with mycoses fungoides, spontaneous remission after infection (Int J Lab Hematol 2007;29:386), with mononucleosis syndrome due to Varicella zoster virus (Eur J Haematol 2002;68:236)
Micro: 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); promonocytes have abundant cytoplasm with delicate granules, nuclei have delicate folds #1; #2; #3; erythrophagocytosis; various images #1; #2; #3
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
Positive stains: CD13, CD14 (most), CD68, CD61 (some)
Negative stains: CD41, glycophorin A
Molecular: 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
DD: AML M4, microgranular acute promyelocytic leukemia, myelodysplastic syndrome (to distinguish, count promonoblasts in M5 with monoblasts), malignant histiocytic disorders
Either erythroleukemia (more common) or pure erythroid leukemia (rare)
One study suggests that most cases may now be defined as AML with multilineage dysplasia (Haematologica 2004;89:ELT11, free full text)
References: eMedicine
Erythroleukemia (M6a)
5% of AML cases; usually adults
20% of therapy related AML but only 1% of de novo AML
Much more common than pure erythroid leukemia (Haematologica 2002;87:148, free full text)
Peripheral smear may have prominent erythroblasts
Criteria for 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
Case reports: 43 year old woman with leukocytosis, congenital disease presenting as liver failure (Archives 2003;127:1362), associated with low dose methotrexate for rheumatoid arthritis (Rheumatol Int 2005;25:311)
Micro: hypercellular marrow; predominance of erythroid precursors which have PAS+ cytoplasmic vacuoles, abnormal nuclear development including megaloblastoid cells, karyorrhexis and gigantoblasts with multiple nuclei; often dysplastic platelets and megakaryocytes with megaloblastoid nuclei; 20%+ of nonerythroid cells are myeloblasts; myeloblasts may have Auer rods; ringed sideroblasts may be present
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); dysplastic erythroid precursor with basophilic stippling; various images #1; #2
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
stains: immature erythroid cells are hemoglobin A+
Positive stains: erythroid cells - glycophorin A (mature forms), hemoglobin A, CD36, CD71, PAS (vacuoles), variable mdr-1 ((Mod Path 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
DD: AML with multilineage dysplasia, megaloblastic anemia, secondary dyserythropoiesis, myelodysplastic syndrome, AML-M2
Pure erythroid leukemia (M6b)
Very rare (3% of acute erythroid leukemia cases)
Also called erythemic myelosis, acute Di Guglielmo syndrome
Aggressive
Case reports: 51 year old man with pancytopenia (Archives 2004;128:241), after essential thrombocythemia (Am J Hematol 2004;77:140), post-myeloma, therapy related (Archives 2006;130:1075)
Micro: 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; abnormal erythroid precursors at all stages of maturation, granulocyte lineage appears normal; very large erythroid precursors; 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), 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; various images #1; #2
bone marrow biopsy: extensive replacement by immature erythroid precursors, with occasional very large abnormal cells
stains: large abnormal cells and others are hemoglobin A+
Enzyme cytochemistry: alpha naphthyl acetate esterase (nonspecific esterase); also acid phosphatase
Positive stains: glycophorin A (mature forms), hemoglobin A, CD36, CD71, mdr1 (Mod Path 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: often complex cytogenetics abnormalities involving #5 and #7
DD: reactive erythroid hyperplasia associated with folate or vitamin B12 deficiency
Acute megakaryoblastic leukemia (AMKL, M7)
Up to 10% of AML in children (common with Down’s syndrome, see below), 5% of adult AML
Associated with marrow fibrosis due to megakaryoblast secretion of fibrogenic cytokines, which makes marrow aspirate difficult to obtain
In adults, median age is 57 years, 59% had prior hematologic disorder or myelodysplastic syndrome, 19% had prior chemotherapy (Blood 2006;107:880)
Criteria for diagnosis: 50%+ blasts of megakaryocyte lineage are present in bone marrow; megakaryocytic lineage based on CD41+ or CD61+ or positive platelet peroxidase reaction on EM
Survival: poor, median overall survival is 6 months
Case reports: 3 year old boy with multiple bruises, 1 year old child, with mediastinal germ cell tumor (Clin Transl Oncol 2007;9:329)
Peripheral blood: often contains micromegakaryocytes and atypical platelets
Micro: megakaryoblasts (often better morphology on biopsy than smear) are medium/large cells with blue vacuolated eosinophilic cytoplasm containing fine granules, cytoplasmic projections resembling platelets, irregular cytoplasmic borders, cytoplasmic zoning; nuclei are round or indented with dense chromatin and 1+ 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; various images #1; #2; #3
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: reticulin stain shows marked increase in reticulin fibers #1; #2; PAS+ large megakaryocytes and micromegakaryocytes, also immature cells and erythrocyte precursors; CD61 #1; #2; #3; #4; #5 (figures C, D); CD34-red, podocalyxin-brown; CD42b (figure c)
Positive stains: CD41 and CD61 (megakaryocyte specific), CD42b (Mod Path 2005;18:603), CD34, CD36, factor VIII, 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 (AJSP 1987;11:883)
Negative stains: myeloperoxidase, Sudan Black B, CD14, CD64, glycophorin A
EM: 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
DD: ALL, AML-M0, M1, M5a, metastatic small blue cell tumors in children, blastic transformation of CML
References: Orphanet (children)
Variant - transient myeloproliferative disorder (TMD) / AMKL in Down’s syndrome
Down’s syndrome patients (trisomy 21) have increased risk for AML, usually AMKL (AML M7)
Transient myeloproliferative disorder (TMD) affects 10% of newborns with Down’s syndrome
TMD usually resolves in 2-14 weeks in neonates, but 20-30% progress to AMKL within 3 years
TMD: early death in 17%, associated with high WBC at diagnosis, increased bilirubin and liver enzymes, failure to normalized WBC (Blood 2006;107:4606)
TMD rarely occurs without Down’s syndrome (Arch Dis Child Fetal Neonatal Ed 1998;79:F215)
Case reports: stillborn fetus with severe disease (Nat Clin Pract Oncol 2007;4:433)
Treatment: less intensive chemotherapy may be effective (J Clin Oncol 2007;25:5442)
Micro: blasts have moderate basophilic cytoplasm with coarse azurophilic granules resembling those in basophils, round to slightly irregular nuclei; also promegakaryocytes, micromegakaryocytes, dyserythropoiesis
Micro images: blasts in transient myeloproliferative disorder of Down’s syndrome; epidermal infiltrate
Peripheral blood: WBC up to 100K with 30-50% blasts, nucleated red blood cells, micromegakaryocytes
Positive stains: CD41, CD61, HLA-DR
Negative stains: CD11b, CD13, myeloperoxidase, Sudan Black B
Molecular: mutations in GATA1 gene in almost all cases (versus 4% of all Down’s syndrome infants, Blood 2007;110:2128), specific mutations may differ in TMD and subsequent AMKL (Int J Hematol 2007;86:250); loss of GATA1 impairs maturation of megakaryocyte erythroid progenitors (Blood 2006;107:87), JAK3 mutations found in 50% (Br J Haematol 2007;137:337)
References: AJCP 2001;116:204, Hum Path 2000;31:396
Acute megakaryoblastic leukemia - t(1;22)(p13;q13) variant
Young children with marked organomegaly (Blood 1991;78:748), prominent myelofibrosis
Tissue involvement resembles metastatic tumor
Poor outcome (Leukemia 2000;14:216)
Case reports: 4 week old infant with hepatic involvement and no initial marrow involvement (Pediatr Dev Pathol 2007 May 16:1 [Epub ahead of print]), with proliferation of erythroid and megakaryocytic lineages (Rinsho Ketsueki 1999;40:230)
Micro: prominent fibrosis, blasts may have spindle shape or form intertwining bundles resembling metastatic disease
References: Atlas of Genetics and Cytogenetics, AJCP 1992;98:214
CD13, CD33 negative acute myeloid leukemia
Not part of WHO classification
Usually AML M1 or M2
Typical myeloid morphology and cytochemistry, but negative for CD13, CD14, CD33, CD61, glycophorin (AJCP 2000;114:29)
Elderly patients negative for CD33 and CD34 have poor prognosis (Cancer 2007 Dec 17 [Epub ahead of print])
May express CD13 or CD33 at relapse (Rinsho Ketsueki 2001;42:314, Intern Med 1993;32:733)
Caution - may be easy to induce CD13 expression with in vitro culture (Southeast Asian J Trop Med Public Health 2002;33 Suppl 2:155)
Molecular: often t(8;21)(q22;q22) (AJCP 1997;107:68, Ann Hematol 1999;78:237)
Rare (<1% of AML); tumor cells have basophilic differentiation
Associated with marrow failure, circulating blasts, skin involvement, organomegaly, hyperhistaminemia symptoms
Diagnosis: may require EM (AJCP 1991;96:160)
Case reports: 18 year old man with 11q23 gene rearrangement (Indian J Pathol Microbiol 2007;50:443), 72 year old man with monosomy 7 (Cancer Genet Cytogenet 2007;172:168), anaphylactoid reaction after chemotherapy (Cancer 1995;75:110)
Treatment: imatinib if bcr-abl present (Ann Biol Clin (Paris) 2006;64:361)
Micro: hypercellular marrow composed of medium sized blasts with high N/C ratio, moderate basophilic cytoplasm with variable number of coarse basophilic granules; nucleus is round, oval or bilobed with 1+ nucleoli; few mature basophils; dysplastic erythroid features
Micro images:
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
Enzyme cytochemistry: myeloperoxidase positive by EM but negative by light microscopy; acid phosphatase positive; negative for Sudan Black B and nonspecific esterase
Positive stains: CD13 and CD33, CD34, HLA-DR; toluidine blue (metachromatic granules), CD203c (Eur J Clin Invest 2001;31:894)
Negative stains: myeloperoxidase by light microscopy
EM: basophilic granules and immature mast cell granules
EM images: granules contain amorphous speckled substance, one granule has a myelin figure
Molecular: often t(9;22) - Philadelphia chromosome
DD: AML-M0 (EM shows no basophilic granules), CML in blast crisis, AML-M2 subtypes with basophilia (Am J Hematol 2004;76:134), acute eosinophilic leukemia, ALL with coarse granules
Myeloid sarcoma - acute leukemia chapter
Also called extramedullary myeloid tumor, granulocytic sarcoma, chloroma if it forms a mass
See also descriptions at various sites in respective chapters
Extramedullary tumor mass of neoplastic immature myeloid (granulocytic or monocytic) cells
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, mediastinum
Case reports: Case of the Week #130 (bone)
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: myeloid tumors - blastic type has myeloblasts with mild/moderate rim of basophilic cytoplasm, fine nuclear chromatin, 2-4 nucleoli; immature type has myeloblasts, promyelocytes and eosinophilic myelocytes; differentiated type has promyelocytes, eosinophilic myelocytes and more mature forms; rarely crystalline inclusions similar to Charcot-Leyden crystals (Archives 2002;126:85)
Cytology: usually background lymphoglandular bodies; Auer rods and eosinophilic myelocytes are rare; resembles large cell lymphoma (Cancer 2000;90:364)
Micro images: differentiated (left) versus blastic types (center and right)-site unknown; various images #1; #2
Myeloid sarcoma - acute leukemia chapter - continued
lymph node - cells have fine chromatin resembling lymphoblastic lymphoma; large blast cells resemble large cell lymphoma, also some eosinophilic myelocytes; tumor cells have irregularly folded and convoluted nuclei; resembles lymphoblastic lymphoma, but has cytoplasmic granules and distinct nuclei; many tumor cells have azurophilic granules; tumor cells mix with residual normal lymphocytes; immature cells with moderate to abundant cytoplasm, round/oval nuclei, distinct and prominent nucleoli, also immature eosinophils
case of the week (bone) - #1; #2; #3; #4; CD45/LCA; CD45RO; CD3; CD34; CD20
other - appendix #1; #2; #3; bladder; breast #1; #2; #3 has blasts with numerous azurophilic granules and promyelocytes, classified as AML with maturation; same tumor with fine needle aspiration; orbital mass with t(8;21) has blasts with immature eosinophils; skin-eosinophilic myelocytes and blasts; small intestine #1; #2; soft tissue of paracervical spine (H&E and CD99); spinal dura-some tumor cells have cytoplasmic granules; testes #1; #2-prominent eosinophilic myelocytes and blasts; intracytoplasmic crystals
stains: chloroacetate esterase-lymph node #1; #2; lysozyme-orbit; myeloperoxidase #1-lymph node; #2-lymph node; #3-mediastinum; #4-breast (left), CD43 (right); CD68 #1-spine; #2-uterus
Myeloid sarcoma - acute leukemia chapter - continued
Positive stains: almost all tumors - lysozyme and CD43; myeloid tumors - myeloperoxidase and CD117; myeloblasts - CD13, CD33 (Archives 2001;125:1448); monocytic tumors - CD68 and variable CD163 (AJCP 2004;122:794); monoblasts - CD14, CD11c (Diagn Pathol 2007;2:42), CD56 (AJCP 2000;114:807) HLA-DR, CD99 (55%, Mod Path 2000;13:452), chloroacetate esterase (Ann Saudi Med 2001;21:287)
Negative stains: CD3, CD20, CD79a, CD34
Cytogenetics: most common are monosomy 7 (11%), trisomy 8 (10%) and MLL rearrangements (9%)
DD: poorly differentiated lymphoma, Burkitt’s lymphoma, small round cell tumors
Myeloid sarcoma of female genital tract - acute leukemia chapter
Rare, but may be initial clinical presentation
Usually ovary, also vagina, cervix
Mean age 40 years, range 13-76 years
Micro: usually diffuse growth pattern, also cords, pseudoacinar spaces; sclerosis common
Micro images: pelvic mass (various images); uterus
Enzyme cytochemistry: chloroacetate esterase, lysozyme, myeloperoxidase, CD68, CD43, CD117
DD: lymphoma, carcinoma, granulosa cell tumor
References: AJSP 1997;21:1156, AJCP 2006;125:783
Acute panmyelosis with myelofibrosis
Also called acute myelofibrosis, acute myelosclerosis, acute myelodysplasia with myelofibrosis
Some question if it is a distinct entity (Ann Hematol 2004;83:513, Leuk Lymphoma 2004;45:681)
Rare, rapid onset, aggressive, usually adults
Weakness, fatigue, bone pain, pancytopenia; usually no marked splenomegaly
Aspirate smear is often hypocellular due to marked fibrosis
Median survival is 2-9 months
Case reports: successful treatment with biphosphonates (Eur J Haematol 2004;73:215)
Micro: hypercellular marrow with erythroblasts, immature granulocytes and megakaryocytes; prominent megakaryocytic abnormalities with variation in size and dysplastic changes, immature granulocytes with dysplasia, immature erythrocytes; usually marked fibrosis (reticulin > collagen)
Micro images:
bone marrow smear (Wright-Giemsa): numerous blasts, some CD61+, 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; various images
bone marrow biopsy: partial replacement of marrow by blasts and increased fibrous tissue; numerous blasts with some clustering
lymph node biopsy: total effacement by blasts, also scattered megakaryocytes at various stages of maturation; blasts have fine chromatin and small but distinct nucleoli, mitotic figures are present
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 and hemoglobin A; granulocytes - myeloperoxidase, CD13, CD33, CD117; monocytes - lysozyme and CD68; megakaryocytes - CD41, CD61, CD31, PAS, factor VIII
Negative stains: usually CD42b (Mod Path 2005;18:603), von Willebrand factor
DD: chronic idiopathic myelofibrosis with myeloid metaplasia (marked splenomegaly and prominent dysplasia), acute megakaryoblastic leukemia (no prominent changes in granulocytes or erythroid cells), myelodysplastic syndrome with myelofibrosis (lacks high % blasts), metastatic carcinoma with desmoplasia
AML with Philadelphia chromosome
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 (AJCP 2007;127:642)
Median survival 9 months
Associated with poor prognosis in biphenotypic leukemia (Haematologica 1999;84:699, free full text)
Case reports: dual presence of t(9;22) and inv(16) (AJCP 2006;125:260), AML-M7 (Ann Hematol 2004;83:381)
Treatment: possibly imatinib, then allogeneic stem cell transplant (Eur J Haematol 2007;79:170)
Micro: 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
References: Wikipedia (Philadelphia chromosome)
AML with pseudo-Chèdiak-Higashi anomaly
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 Chediak-Higashi syndrome in Bone Marrow-Nonneoplastic chapter
Case reports: 16 year old Chinese girl with AML M5a and t(10;11) (Clin Lab Haematol 2000;22:303)
Micro: giant cytoplasmic granules
Micro images: specific granules resemble Chediak-Higashi anomaly #1; #2; in blast cells in AML-M2 patients; acute promyelocytic leukemia #1; #2
Chediak-Higashi syndrome (for comparison): #1; #2
Positive stains: CD2 (AJCP 2006;125:791)
Cytogenetics: may be associated with double minutes (Leukemia 2002;16:152)
EM: 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)
Hypocellular AML
Not part of WHO classification
Up to 10% of AML cases
Median age 67 years (Leuk Res 1996;20:563)
Defined by WHO as <20% bone marrow cellularity, 20% or more are blasts, other definitions range up to 40% cellularity
Rare blasts in peripheral blood
Often has smoldering course, although intensive chemotherapy may cause complete remission
Case reports: elderly patients (Nippon Ronen Igakkai Zasshi 1997;34:70)
Micro images: markedly hypocellular marrow in 57 year old man with severe pancytopenia and rare blasts in blood #1; #2-cells in interstitium are predominantly blasts; various images
Positive stains: myeloperoxidase
DD: substance abuse (Archives 2005;129:e35), refractory anemia with excess blasts, aplastic anemia (no excess blasts, interstitial bone marrow cells are plasma cells, lymphocytes and mast cells, not blasts)
ALL
Acute lymphoblastic leukemia (ALL) - general
5200 cases/year in US (National Cancer Institute), peaks at age 4, usually age 15 years or less
80% of childhood leukemia is ALL
Higher incidence in whites, males, 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’s 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, no circulating blasts
Laboratory: anemia common, platelet count < 100K in 75% and <10K in 15%; leukopenia (25%), WBC > 100K (10%)
Cytogenetics / FISH is single most important prognostic factor for adults (Blood 2007 Dec 21 [Epub ahead of print])
Favorable prognosis: age 2-10 years, female, white; preB phenotype, hyperdiploidy >50, t(12,21), normal WBC count at presentation, rapid response to chemotherapy, CD10+
Intermediate prognosis: hyperdiploidy 47-50, diploid, 6q-, 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, AJCP 2002;117:716); hypodiploidy, near tetraploidy, 17p-, t(11q23); CD10 negative preB ALL; 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)
Diagnosis: immunostains required for diagnosis
Case reports: mature phenotype but non-L3 morphology (Mod Path 2004;17:832)
Treatment: children - multiagent chemotherapy plus CNS chemotherapy; 90% go into remission, 2/3 are cured; thrombopoietin may induce CML like changes (AJCP 2002;117:844); adults - choice of chemotherapy or stem cell transplantation is not clear (Hematology Am Soc Hematol Educ Program 2007;444)
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%), evolve to AML; CNS relapse common
Acute lymphoblastic leukemia (ALL) - general - continued
Micro: blasts have scant agranular cytoplasm, no Auer rods, coarse to fine chromatin, often indistinct nucleoli, no dysplastic myeloid cells
Peripheral smear: leukoerythroblastosis common with granulocyte precursors and nucleated RBCs, lymphoblasts, occasionally reactive lymphocytes, rarely marked eosinophilia
Bone marrow: hypercellular, high percentage of lymphoblasts
Micro images:
Peripheral smear images: blasts with scant cytoplasm and prominent nucleoli
L1 type (blood smears): blasts have minimal cytoplasm, variable nuclear size and chromatin density, irregular nuclear contour, some small nucleoli; blasts have moderate cytoplasm, round nuclei of variable size, coarse chromatin, some resemble mature lymphocytes
L1 type (bone marrow smears): blasts contain large cytoplasmic azurophilic granules (uncommon), but were B cells by IHC and cytochemistry
L1 type (bone marrow biopsy): markedly hypercellular marrow with lymphoblasts replacing normal marrow elements; lymphoblasts occupy marrow, have minimal cytoplasm and indistinct cell borders, convoluted nuclei, angulated borders; lymphoblasts are small with more condensed chromatin; 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 moderate cytoplasm, large nuclei with coarsely reticular chromatin, 1-3 prominent nucleoli; lymphoblasts have variable size, moderate cytoplasm, markedly irregular nuclei with coarse chromatin and distinct nucleoli; most lymphoblasts have variable size, reticular chromatin with prominent nucleoli, some have L1 features; 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, prominent nucleoli
Acute lymphoblastic leukemia (ALL) - general - continued
L3 type (bone marrow smears): no prominent vacuoles, dispersed chromatin and more obvious nucleoli than usually observed in L3, diagnosed as ALL-L3, non-Burkitt’s type
L3 type (stains): strong cytoplasmic staining by methyl green pyronine (left), vacuoles are Oil Red O positive (right)
Lymph node (aspirate smear): lymphoblasts and some lymphocytes
Other: various images; relapsed ALL; CNS relapse of ALL; refractory ALL
Children: 80% are L1, 10-20% L2, <5% L3
Adults: 35% are L1, 60% L2, <5% L3
Enzyme cytochemistry: negative for myeloperoxidase, chloroacetate esterase, nonspecific esterase (usually), only rarely positive for Sudan Black B (Mod Path 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, CD34
Negative stains: myeloperoxidase (usually, but positive in 23% of adults using a polyclonal antibody, AJCP 2001; 116:25)
Note: TdT negative cases may demonstrate early T-cell lineage by flow cytometry (Archives 2000;124:92)
Cytogenetics: 90% have cytogenetic abnormalities, usually hyperdiploidy (>50 chromosomes), also pseudodiploidy (46 chromosomes but structural anomalies), t(12,21); t(9,22) [Philadelphia chromosome], t(4,11)
EM images:
DD: AML, hematogones (normal B lymphoid precursors, AJCP 2000;114:66), reactive lymphocytosis, hypoplastic anemia, CLL, adult T cell leukemia, AML-M3, non-Hodgkin’s lymphoma, Merkel cell carcinoma (may be TdT+, Mod Path 2007;20:1113)
WHO classification system includes former FAB classifications ALL-L1 and L2
FAB L3 is now considered Burkitt’s lymphoma
WHO classification of Acute Lymphoblastic Leukemia
Precursor B lymphoblastic leukemia / lymphoblastic lymphoma
- ALL with t(9;22)(q34;q11) (BCR-ABL-Philadelphia chromosome)
- ALL with t(v;11q23) (MLL rearranged)
- ALL with t(1;19)(q23;p13) (PBX-E2A)
- ALL with t(12;21)(p13;q22) (TEL-AML1)
- Hyperdiploid > 50
- Hypodiploid
Precursor T lymphoblastic leukemia / lymphoma
References: Mod Path 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, 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, 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+, PAS -; cytoplasm is methyl green-pyronine positive
Not part of WHO classification
ALL with marked eosinophilia is rare (<50 cases reported thru 2005), but may obscure ALL diagnosis
Symptoms are related to hypereosinophilia, including respiratory failure, myocardial infarction, cerebrovascular accident (Leuk Lymphoma 2005;46:1045)
Eosinophilia resolves with remission, returns with relapse
Eosinophilia is usually reactive, not part of leukemic cells
Treatment: steroids suppress eosinophlia
Case reports: t(5;9) with detection of residual disease in CSF by PCR (Archives 2003;127:601); prior idiopathic hypereosinophilic syndrome (Leuk Res 2005;29:975), prior eosinophilic myelodysplasia (J Clin Pathol 1999;52:388), T-ALL with eosinophilia and AML (Cytometry B Clin Cytom 2005;65:37), 10 year old with urticaria (J Am Acad Dermatol 2004;51:S151), 5q- deletion (Pediatr Dev Pathol 2003;6:558)
Molecular: may have t(5;14)(q31;q32) - IL3 and IgH (Atlas of Genetics and Cytogenetics)
Micro images: bone marrow smear shows blasts, eosinophilic myelocytes, granulocytes and normoblasts; CSF shows prominent eosinophilia, basophilia and rare blasts (center)
PreB ALL
Precursor-B cell acute lymphoblastic leukemia (ALL) / lymphoblastic lymphoma (LBL) - acute leukemia chapter
See also Lymphomas: B cell chapter
Also called B cell acute lymphoblastic leukemia / lymphoblastic lymphoma
Usually children
Pre 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, testicular involvement
Pre B acute lymphoblastic lymphoma often presents with cutaneous nodules, bone or nodal involvement, but NO marrow involvement
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 (AJCP 2007;127:39)
Best prognosis: age 2-10 years, early preB phenotype, hyperdiploidy, t(12,21)
Worse prognosis: less than 2 years, older than 10 years, t(9;22), CD10 negative or expression of myeloid antigens
Case reports: arising from follicular lymphoma (Archives 2002;126:997), with basal cell carcinoma (Diagn Pathol 2007;2:32), mature phenotype but no translocations (Archives 2003;127:1340), 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: bone marrow smears - intermediate sized blast-like cells with scant, variably basophilic cytoplasm, round/oval or convoluted nuclei, fine chromatin, indistinct nucleoli; frequent mitotic figures; may have “starry sky” appearance similar to Burkitt’s lymphoma; may have large lymphoblasts with 1-4 prominent nucleoli resembling myeloblasts; usually no sclerosis
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
Precursor-B cell acute lymphoblastic leukemia (ALL) / lymphoblastic lymphoma (LBL) - continued
Micro images:
peripheral blood: blasts with scant cytoplasm but prominent nucleoli; L1 type has smaller blasts with minimal cytoplasm, coarse chromatin, some cleaved nuclei or irregular contours, no distinct nucleoli; blasts have L1 morphology, but mature phenotype
bone marrow smears: various images #1; #2; #3; #4; #5
lymphoblastic lymphoma: skin and marrow; 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: #1; #2; #3: TdT+; #4: CD79a+; #5: CD34+
Positive stains: TdT (negative in 3%, AJCP 2004;121:810), CD19, CD22, CD79a; CD34 (75%), usually cytoplasmic (not surface) immunoglobulin but rarely surface immunoglobulin (AJCP 2004;121:512), also CD9, CD24, CD38, CD45, 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 (AJCP 1999;111:467)
Negative stains: cytoplasmic IgM, CD15, CD30
Flow cytometry images: various images
Molecular: usually chromosomal abnormalities
DD (based on morphology): Burkitt’s lymphoma, granulocytic sarcoma, blastic variant of mantle cell lymphoma, Ewing’s sarcoma (negative for CD79a, CD43, TdT and immunoglobulin or T cell receptor rearrangement, vimentin++), Hodgkin’s lymphoma, AML (prominent nucleoli, delicate chromatin, fine azurophilic cytoplasmic granules)
PreB ALL with t(9;22)(q34;q11)
ALL with bcr-abl fusion transcript (Philadelphia chromosome)
30% of adults with ALL, 4% of children but 80% of infants
Older age and higher WBC at presentation than other preB ALL (excluding infants)
May have more organomegaly or CNS involvement than other preB ALL
Poor prognosis
Treatment: tyrosine kinase inhibitors 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: no defining morphology, but large blasts with prominent nucleoli and cytoplasmic granules are more common than other preB-ALL
Micro images: leukemic cells resemble early erythroblasts; various images
Cytology images - contributed by Dr. Julia Braza, Beth Israel Deaconess Medical Center, Boston, Massachusetts (USA) - CSF #1; #2; #3
Positive stains: myeloid antigens in 71% (AJCP 1999;111:467)
Molecular: translocation involves abl on #9q34 (tyrosine kinase) and bcr on #22q11 (breakpoint cluster region)
FISH images - contributed by Dr. Julia Braza, Beth Israel Deaconess Medical Center, Boston, Massachusetts (USA) - bcr-abl FISH probe
Molecular images: drawing of translocation; karyotype
PreB ALL with t(v;11q23)
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 be bilineal with monoblasts and promonocytes
Usually infants < 1 year with markedly increased WBC, CNS involvement
Poor prognosis (30% event free survival)
Treatment: intensive chemotherapy followed by hematopoietic stem cell transplantation
Micro: no defining morphology
Positive stains: TdT, CD19, CD34, HLA-DR; also CD15, often myeloid antigens CD13 and CD33 (AJCP 1999;111:467)
Negative stains: CD10
Molecular: most translocations at 11q23 involve MLL (mixed lineage leukemia) gene; over 75 genetic arrangements; t(4;11)(q21;q23) - MLL-AF4 occurs in 60% of infants, 2% of other children, 3-6% of adults; also t(11;19)(q23;p13.3) - MLL-ENL and others
Molecular images: diagram of ALL1/MLL duplication
References: Atlas of Genetics and Cytogenetics
PreB ALL with t(1;19)(q23;p13)
Commonly detected by conventional cytogenetics in children
5-6% of ALL
High WBC counts, frequent CNS involvement
In children, is no longer a poor prognostic factor (Blood 1984;63:721), due to intensive therapy and bone marrow transplantation; in adults, is associated with short survival (Leuk Lymphoma 2006;47:469)
Case reports: t(1;19) without fusion transcript by PCR or Southern blot (Rinsho Ketsueki 2005;46:7), 5 year old boy with splenomegaly and neurologic symptoms
Micro: no distinct morphologic findings
Positive stains: CD9, CD10, CD19
Molecular: produces fusion transcript of PBX 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)
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) #1 with loss of der(1)t(1;19); #2
References: Mol Cell Biol 1994;14:3938, Atlas of Genetics and Cytogenetics
PreB ALL with t(12;21)(p13;q22)
20-30% of childhood preB ALL (most common translocation, Chin Med J (Engl) 2003;116:1298) and 3% of adults
5 different patterns of gene expression involving 14 genes, detected with gene chip (BMC Genomics 2007;8:385)
Excellent prognosis due to good response to chemotherapy; almost 100% remissions
Persistence of TEL-AML1 transcripts is not necessarily related to relapse (Pediatr Int 2003;45:275)
Micro: no distinct morphology
Positive stains: CD10 (bright), HLA-DR; also CD13 and CD33 (Diagn Mol Pathol 2000;9:184)
Negative stains: CD9, CD20
Molecular: fusion of TEL/ETV6 and AML1/RUNX1/CBFA2 genes; not found by conventional cytogenetics (cryptic) because rearranged segments are too small; detect with FISH or PCR; may have no other molecular abnormalities, almost never > 50 chromosomes
References: Atlas of Genetics and Cytogenetics
PreB ALL with hyperdiploidy with > 50 chromosomes
“High hyperdiploidy” means >50 chromosomes
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 preB ALL
Favorable overall survival (Am J Hematol 2007;83:34), although outcome in children varies by specific trisomy present (Blood 2003;102:2756)
Micro: no distinct morphology
Molecular: mutations in NRas (10%), FLT3 (9%), PTPN11 (9%) and KRas (6%) (Genes Chromosomes Cancer 2008;47:26)
PreB ALL with hypodiploidy
5% of preB ALL
Most have 45 chromosomes, fewer chromosomes is rare
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), <45 versus 45 chromosomes (Cancer 2003;98:2715)
Overall 50% survival at 8 years
Micro: no distinct morphology
Molecular: defined as fewer than 45 or 46 chromosomes
Cytogenetic images: karyotype of severe hypodiploidy
Mature B cell ALL - acute leukemia chapter
Also called Burkitt’s leukemia, FAB L3
See also Lymphoma-B cell chapter for Burkitt’s lymphoma
WHO classifies Burkitt’s 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 (Archives 2003;127:1340)
Case reports: 53 year old woman with hepatosplenomegaly (Archives 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: 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 aspirate (fig 1B), bone marrow biopsy (fig 2), inset-CD20; Burkitt’s lymphoma
peripheral blood smears: large cells with prominent vacuoles #1; #2
bone marrow smears: large cells with basophilic cytoplasm and vacuoles #1; #2; #3
stains: Oil Red O+
Positive stains: CD10, CD19, CD20, CD22, CD79a; bright surface immunoglobulin with light chain restriction (overall is mature B cell phenotype); Oil Red O
Negative stains: CD5, CD23, CD34, TdT
Molecular: c-myc gene amplification with t(8;14), t(2;8) or t(8;22)
Other ALL
Precursor T cell acute lymphoblastic leukemia (T-ALL) / lymphoma (T-LBL) - acute leukemia chapter
Also called T cell acute lymphocytic leukemia
See also Lymphoma non B cell chapter
Teens and young men (older than preB ALL)
Most cases begin after birth (Blood 2007;110:3036)
T-ALL versus T-LBL: T-ALL has a more immature phenotype, CD47 expression, no 11q23 rearrangement (Pediatr Blood Cancer 2006;47:130), a 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)
PreT ALL constitutes 15% of childhood and 20-25% of adult ALL cases
PreT LBL constitutes 85-95% of LBL, usually presents as mediastinal mass with no/minimal marrow involvement
CNS involvement if untreated
Comparison of younger (age 16-60 years) vs. older involvement (61+ years): more hepatosplenomegaly, presents with mediastinal mass and lymphadenopathy; myeloid antigens and lineage inappropriate gene rearrangements are less common (AJCP 2002;117:252)
Good prognostic factors: HOX11 overexpression in adults (AJCP 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)
Diagnosis: T-ALL if lymphoblasts are 25% or more of marrow cells or no mass lesion; T-LBL otherwise
Case reports: 25 year old man with hemoptysis
Treatment: chemotherapy cures 60%; earlier relapse and poorer prognosis than preB ALL, often in CNS
Micro: 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
Micro images:
blood smear shows markedly elevated leukocyte count with variable lymphoblast size and chromatin density; various images #1; #2; #3; #4
L1 type (blood smears) - moderate cytoplasm with variable basophilia, coarse chromatin; various images
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
stains: focal paranuclear acid phosphatase staining
Precursor T cell acute lymphoblastic leukemia / lymphoma (preT ALL/LBL) - continued
Positive stains: CD1, 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%), CD57, CD79+ (40-60%, AJCP 2000;113:823), CD117 (12%, Exp Mol Pathol 2006;81:162)
Negative stains: CD19, CD20
Note: ALL with aberrant myeloid antigen expression is correct name, not biphenotypic leukemia
Molecular: different cytogenetic abnormalities than B-ALL, 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
DD: Burkitt’s leukemia (B cell phenotype), granulocytic sarcoma (positive for myeloid markers), lymphoblastoid mantle cell lymphoma (B cell phenotype), thymoma (AJCP 2004;121:268)
References: Atlas of Genetics and Cytogenetics, Stanford University
Defined as two separated blast populations, one myeloid and the other lymphoid, or rarely one B cell and one T cell
Acute bilineal and biphenotypic leukemias are less than 4% of acute leukemias
Often poor prognosis
Case reports: t(9;17)(p11;q11) (Leuk Lymphoma 1997;25:179)
Cytogenetics: B cell plus myeloid cases may have t(9;22)(q34;q11.2) or 11q23 translocations or del(9); T cell plus myeloid cases may have 2p13 translocations or other unrelated anomalies (Leukemia 2007;21:2264)
Cytogenetics images: t(4;11)(q21;23) in bilineal leukemia
DD: ALL or AML with aberrant antigen expression
<4% of acute leukemias
Also called acute mixed lineage leukemia
Single population of blasts expresses myeloid, and usually either B or T cell antigens; expression of B & T or B, T & myeloid antigens is rare
May derive from primitive stem cell with capacity to express markers of both myeloid and lymphoid lineage
Either de novo or therapy related
European Group for the Immunological Characterization of Leukemias has developed a scoring system based on degree of lineage specificity of each antigen (Haematologica 1997;82:64-scoring system, Leukemia 1995;9:1783)
Scoring system: diagnosis requires score greater than 2 from 2 separate lineages:
2 points: B cell - CD79a, CD22, cytoplasmic IgM; T cell - CD3; myeloid - myeloperoxidase by cytochemistry or IHC
1 points: B cell - CD19 or CD10, T cell - CD2 or CD5, myeloid - CD13 or CD33
0.5 points: B cell - TdT, T cell - TdT or CD7, myeloid - CD14, CD15, CD11b or CD11c
Often poor prognosis
Case reports: 80 year old man with blasts coexpressing CD79a and myeloid markers (Archives 2003;127:356), with myeloid, B cell and NK phenotype (Archives 2003; 127:E93), due to transformation of essential thrombocythemia (Am J Hematol 2006;81:624), 58 year old woman with pancytopenia
Treatment: usually based on morphology of blasts
Micro: no consistent morphology; myeloid features usually resemble AML-M1 (without differentiation) or AML-M5 (monoblastic / monocytic)
Micro images: 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 #1; #2-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); various images
Positive stains: by definition, express myeloid and lymphoid markers; most specific markers are - B cell: CD79a, CD22 and cytoplasmic Ig; T cell - CD3 and anti-T cell receptor; myeloid - myeloperoxidase (cytochemistry or flow cytometry)
Flow cytometry images: biphenotypic acute leukemia with CD19 and myeloperoxidase coexpression (figure B)
EM images: monocytoid blast has folded nucleus and scattered small electron dense granules
Molecular: often complex abnormalities, most common are t(9;22) and 11q23 changes; also 2p13 or other abnormalities (Leukemia 2007;21:2264)
DD: ALL or AML with aberrant antigen expression
References: Atlas of Genetics and Cytogenetics
End of Leukemia-acute chapter