Bone marrow neoplastic

Bone marrow - neoplastic myeloid

AML not otherwise specified

AML without maturation (FAB AML M1)



Last author update: 1 February 2013
Last staff update: 10 February 2022

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PubMed Search: Acute myeloid leukemia [title] without maturation FAB AML M1


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Cite this page: Mihova D. AML without maturation (FAB AML M1). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/leukemiaM1.html. Accessed January 30th, 2023.
Definition / general
  • 10 - 20% of AML cases, 44% in one Brazil hospital (Sao Paulo Med J 2006;124:45)
  • Usually adults (median age 46 years), present with anemia, thrombocytopenia and neutropenia; may have leukocytosis with markedly increased blasts
  • 4% of childhood AML
Clinical features
  • Criteria for diagnosis: 90%+ of nonerythroid cells in marrow are myeloblasts; < 10% granulocytic elements; 3%+ of blasts must be positive for myeloperoxidase or Sudan Black B and / or Auer rods by enzyme cytochemistry
  • Enzyme cytochemistry: 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
  • Poor prognosis
Case reports
Microscopic (histologic) description
  • Typically markedly hypercellular marrow, but normocellular and hypocellular cases occur
  • Very immature cells, usually round with few azurophilic cytoplasmic granules or Auer rods
  • Nuclei are round or indented; little maturation beyond myeloblast stage
  • Cells may may resemble lymphoblasts and not appear myeloid
Microscopic (histologic) images

AFIP images
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Blasts show mild size variation

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Blasts show more variation in size and number of nucleoli

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Myeloblasts have irregular nuclei

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Myeloblasts have marked size variation

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Some variation in size

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Large myeloblasts
with abundant
eosinophilic
cytoplasm


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Agranular myeloblasts

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Bone marrow biopsy

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Peripheral blood smear

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Myeloblasts are myeloperoxidase+

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Numerous granules are Sudan black B+

Positive stains
Negative stains
Molecular / cytogenetics description
Electron microscopy description
Electron microscopy images

AFIP images
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Numerous electron dense granules in Golgi region

Differential diagnosis
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