- 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
- 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
- 4 year old child with t(6;9) and basophilia (Ann Biol Clin (Paris) 2003;61:352)
- 44 year old man with large and small blasts (Arch Pathol Lab Med 2004;128:448)
- Presenting with arterial thromboembolism (Leuk Res 2007;31:869)
- 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
Bone marrow smears (Wright-Giemsa):
Blasts show mild size variation, have pale
to slightly basophilic agranular cytoplasm
and uniform nuclei with fine chromatin
and prominent nucleoli
Blasts show more variation in size and
number of nucleoli, four blasts have
Auer rods
Myeloblasts have irregular nuclei with folding and
invagination, one myeloblast has numerous
azurophilic granules
Myeloblasts have marked size variation,
irregular nuclei with condensed chromatin,
no nucleoli, one blast has a thin Auer rod
Some variation in size, two myeloblasts
have more intense basophilic cytoplasm
and coarse nuclear chromatin
Myeloblasts are large with abundant eosinophilic
cytoplasm, 2 cells have prominent Auer rods, 1
has azurophilic granules and 2 erythroblasts
Agranular myeloblasts have variation in size,
cytoplasmic volume and cytoplasmic basophilia
Bone marrow biopsy:
Marrow is completely replaced by blasts
with variable cytoplasm, round / oval nuclei
with mild irregularities and small / indistinct
nucleoli
Peripheral blood smear:
Case with inv(3)(q21q26) shows large and
smaller blasts and normal appearing platelets
Stains:
Myeloblasts are myeloperoxidase+
Numerous granules are Sudan Black B+
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Bone marrow biopsy:
Biphasic morphology (large and small blasts)
- cCD3, CD14 (usually), CD15, cCD22, CD36 (usually), CD41, CD61, CD64 (usually, Arch Pathol Lab Med 2007;131:748), CD65, cCD79a and glycophorin A
- Associated with t(8;21)
- FLT3 ITD in 22% (Ai Zheng 2007;26:58)
- FLT3 mutations associated with HLA-DR negative patients (Leuk Res 2007;31:921)
- May have heterogeneous features (Ultrastruct Pathol 1995;19:9)
Numerous electron dense granules in Golgi region,
also granules throughout cytoplasm and prominent nucleolus
