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

Author: Daniela Mihova, M.D. (see Authors page)

Revised: 3 April 2018, last major update March 2013

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PubMed Search: Acute myeloid leukemia with minimal differentiation FAB AML M0

Cite this page: Mihova, D. Acute myeloid leukemia with minimal differentiation (FAB AML M0). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/leukemiaM0.html. Accessed August 20th, 2018.
Definition / general
  • No definitive evidence of myeloid differentiation by morphology and light microscopy cytochemistry; need immunohistochemistry, flow cytometry, or EM cytochemistry to characterize as myeloid
  • Criteria for diagnosis: nongranular blasts; less than 3% of blasts are positive for myeloperoxidase (MPO), Sudan Black B (SBB) or naphthol-ASD-chloroacetate esterase (CAE) by enzyme cytochemistry, although blasts may express myeloperoxidase by EM or immunohistochemistry; blasts do not express classic lymphocyte antigens, but may aberrantly express some lymphocyte antigens
Clinical features
  • 5% or less of AML cases; any age, mostly infants or older adults
  • Typically presents with anemia, thrombocytopenia, neutropenia, marrow failure, but may have leukocytosis with markedly increased blasts
  • Children (Blood 2007;109:2314) and adults (Br J Haematol 2001;113:737) may have poorer outcome than other AML subtypes
  • Enzyme cytochemistry: negative for nonspecific esterase, although may have nonspecific weak or focal reaction distinct from monocytic cells
Case reports
Microscopic (histologic) 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
Microscopic (histologic) images

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



Bone marrow biopsy:
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Complete replacement of marrow
by blasts without differentiation



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



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

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M0 (figure A) compared to other AML



Stains:
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Blasts are positive for myeloperoxidase by IHC

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CD99

Flow cytometry description
Flow cytometry Images

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Various gating plots

Positive stains
Negative stains
Molecular / cytogenetics 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

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Granules are myeloperoxidase positive



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Granules are myeloperoxidase positive

Differential diagnosis