Bone marrow neoplastic
Bone marrow - neoplastic myeloid
AML not otherwise specified
AML M5


Topic Completed: 1 February 2013

Minor changes: 18 June 2020

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PubMed Search: Acute monoblastic and acute monocytic leukemia AML M5

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Cite this page: Mihova D. AML M5. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/leukemiaacutemonocyticleukemia.html. Accessed August 10th, 2020.
Definition / general
Diagnosis
  • 80% or more nonerythroid bone marrow cells are monocyte lineage (monoblasts, promonocytes and monocytes)
  • A minor neutrophil component < 20%
Microscopic (histologic) images

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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
Molecular / cytogenetics description
  • 11q23 translocations in 19%, trisomy 8 in 17%
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