Acute megakaryoblastic Leukemia.
Acute megakaryoblastic leukemia is a rare and rapidly fetal disorder characterized by extensive proliferation of megakaryoblasts and  atypical megakaryocytes in bone marrow and extramedullary sites, thrombocytopenia and only a few blasts in peripheral blood. Three cases of this leukemia were studied morphologically, cytochemically, and electron microscopically. The leukemia blasts varied from 10-20 mu in diameter, had coarsely reticular nuclear chromatin, and numerous cytoplasmic projections and vacuoles. Except for intense granular PAS positivity and diffuse acid phosphatase reactivity, all of the usual cytochemical stains were negative. The blasts had no specific differentiating features identifying them as megakaryoblasts even at the ultrastructural level. In such instances demonstration of platelet peroxidase will confirm the megakaryocytic origin. All three patients in this series were men and all died within 90 days. Two patients also had other malignancies.
D000208:Acute Disease; D000368:Aged; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000648:ultrastructure; D008854:Microscopy, Electron; D008875:Middle Aged; D013920:Thrombocythemia, Essential / Q000473:pathology*