Home   Chapter Home   Jobs   Conferences   Fellowships   Books


Leukemia - Acute

AML not otherwise categorized

Acute myeloid leukemia with minimal differentiation (FAB AML M0)

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


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

Clinical features

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

Case reports

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

Micro description

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

Micro images

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

M0 (figure A) compared to other AML

Bone marrow biopsy:

Complete replacement of marrow by blasts without differentiation

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

Flow cytometry description

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

Flow cytometry images

Various gating plots

Positive stains

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

Negative stains

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

Molecular description

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

Electron microscopy description

● Resembles myeloblasts; may show focal myeloperoxidase+ granules

Electron microscopy images

Granules are myeloperoxidase positive

Differential diagnosis

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

End of Leukemia - Acute > AML not otherwise categorized > Acute myeloid leukemia with minimal differentiation (FAB AML M0)

This information is intended for physicians and related personnel, who understand that medical information is often imperfect, and must be interpreted in the context of a patient's clinical data using reasonable medical judgment. This website should not be used as a substitute for the advice of a licensed physician.

All information on this website is protected by copyright of PathologyOutlines.com, Inc. Information from third parties may also be protected by copyright. Please contact us at copyrightPathOut@gmail.com with any questions (click here for other contact information).