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Leukemia - Acute

AML not otherwise categorized

Acute myeloid leukemia with maturation (FAB AML M2)


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

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

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

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

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

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


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

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

Bone marrow biopsy:

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

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

Flow cytometry description
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Clinical Flow Wiki

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

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

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

Electron microscopy images
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Numerous primary granules and fusion of Auer rods

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

End of Leukemia - Acute > AML not otherwise categorized > Acute myeloid leukemia with maturation (FAB AML M2)


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