A subtype of acute myelogenous leukemia.
Evolves from early megakaryoblastic precursors.
More frequent in children, especially those with Down’s syndrome.
In adults associated with chemotherapy exposure, or a previous myeloproliferative disorder.
Represents 3-14% of all cases of AML.
About 65% adult cases associated with myelofibrosis.
Symptoms related cytopenias and organomegaly.
Peripheral smear shows megakaryoblasts, giant abnormal platelets, leukopenia, anemia and nucleated red blood cells.
Bone marrow has fibrosis and is difficult to aspirate.
Bone marrow biopsy shows hypercellularity with clusters of megakaryocytes.
Marrow stains for myeloxidase, Sudan black and non-specific esterase are negative differentiating this lesion from other acute myelogenous leukemias.
Platelet antigens are expressed on blasts:CD61, factor VIII, CD42b, and CD41.
t(1;22) translocation found in one third of cases in children and infants.
Adults often have complex chromosomal abnormalities including:3,-5q, or -7q, and t(9;22).
Treatment is with standard induction chemotherapy for AML, with 50% complete remission rate and overall survival of less than 10 months.