Acute megakaryoblastic leukemia simulating carcinoma

Acute megakaryoblastic leukemia has emerged as an important subset of early childhood leukemia. It often presents a diagnostic dilemma because of its many morphologic manifestations and propensity to mimic metastatic carcinoma. An abdominal mass was identified by sonographic and computed tomographic scans in a 10-month-old girl, who had anemia and thrombocytopenia. An open biopsy of the 3-cm, peripancreatic mass showed cohesive nests and sheets of tumor cells with focal spindling and desmoplasia. Although the diagnosis of acute megakaryoblastic leukemia was established from a bone marrow aspirate using immunocytochemical techniques and karyotype analysis, a coexistent abdominal epithelial malignant neoplasm could not be excluded entirely by light microscopic examination alone. The megakaryoblastic nature of the abdominal tumor was established by immunocytochemical stains for glycoprotein IIIa on paraffin-embedded tissue.