AML M7 – Acute Megakaryoblastic Leukaemia

Acute megakaryoblastic leukemia is uncommon. There is a predominance of bone marrow cells of the megakaryocyte lineage.
It is commonly associated with patients with Down Syndrome, and this entity is classified as myeloid leukemia associated with Down syndrome.

Diagnostic Criteria (WHO 2016)

• Blast ≥ 20% in the peripheral blood or bone marrow
• ≥ 50% are of megakaryocyte lin­eage in bone marrow

Blood Film Features:

• Megakaryoblasts: large cells, irregular nucleus, basophilia cytoplasm, usually agranular with cytoplasmic blebs
• Dysplastic large platelets with irregular borders
• Patients may present with pancytopaenia given underlying bone marrow fibrosis

Bone Marrow Features:

• May be a dry tap – due to marrow fibrosis
• Megakaryoblasts – often in small clusters
• Dysmegakaryopoiesis – Micromegakaryocytes
• Cytochemistry: Myeloperoxidase – Negative, Sudan Black B – Negative, Specific Esterase – Focal positivity

Other features to look for:

• Dysplasia in other lineages

Other Resources

• ASH image bank: Acute megakaryoblastic leukemia
• Clinical Flow Wiki: Acute Megakaryoblastic Leukemia (AMKL) (M7)