Platelet vacuoles in acute megakaryoblastic leukemia

The case of a 53-year-old man with acute megakaryoblastic leukemia (M7) was studied. At time of diagnosis, the platelet count was 980 X 10(9)/L and abnormal platelet vacuoles were present. The vacuoles were periodic acid-Schiff (PAS) positive. Electron microscopic examination showed large aggregates of glycogen. Findings of qualitative platelet function studies were abnormal. The authors' study and review of the literature indicates that thrombocytosis with large platelet vacuoles accompanying a blast cell population suggests a diagnosis of M7 and indicates the need for appropriate confirmatory studies.