[Cytological features and prognosis of megakaryoblastic leukemia]

Nine patients with acute leukemia showing 10% or more positive blast cells with platelet peroxidase (PPO) or CD41b were diagnosed as megakaryoblastic leukemia. Three patients transformed from myelodysplastic syndromes or myeloproliferative disorders. The PPO positivity ranged from 7 to 55% (median 45%), and that for CD41b was 1.6 to 67.0% (median 16.4%). Because electron microscopic myeloperoxidase or glycophorin A were also positive in some patients, and also because CD41b positivity was often discordantly lower than PPO positivity, a possibility of mixed leukemia demonstrating myeloid or erythroid differentiation was suggested in 6 of these cases. As for the treatment results, all 3 pediatric cases who received combination chemotherapy achieved complete remission (CR). Among 6 adult cases CR was obtained in only one patient to whom low-dose cytosine arabinoside was administered. The remaining adult patients who received combination chemotherapy died relatively early.