title: Acute megakaryoblastic leukemia. Blast cell aggregates simulating metastatic tumor.
abstract: Acute megakaryoblastic leukemia is a rare leukemia that can present diagnostic problems. We describe two children who have this disease and had clumps of blast cells in their bone marrow, a finding usually attributed to metastatic tumor. The megakaryocytic origin of the cells was supported by their cytochemical staining pattern (positive alpha-naphthyl acetate esterase resistant to sodium fluoride inhibition and negative alpha-naphthyl butyrate esterase) and by the presence of factor VIII-related antigen. Ultrastructural studies of blast cells from one patient demonstrated platelet peroxidase. The mechanism of blast cell clump formation in these cases is unknown; nevertheless, awareness that this feature can occur in acute megakaryoblastic leukemia may avoid a misdiagnosis of metastatic solid tumor.
mesh_terms: D000208:Acute Disease; D000941:Antigens / Q000032:analysis; D001853:Bone Marrow / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D002448:Cell Adhesion; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005169:Factor VIII / Q000032:analysis / Q000276:immunology; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000473:pathology; D009362:Neoplasm Metastasis / Q000473:pathology*; D013920:Thrombocythemia, Essential / Q000175:diagnosis / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D014841:von Willebrand Factor
chemical_list: D000941:Antigens; D014841:von Willebrand Factor; D005169:Factor VIII