ACUTE MEGAKARYOBLASTIC LEUKEMIA IN CHILDREN AND ADOLESCENTS - A RETROSPECTIVE ANALYSIS OF 24 CASES

In order to characterize the clinical, cytogenetic, and outcome featur es of childhood acute megakaryoblastic leukemia (AMKL), we reviewed 24 cases; 14 were identified among 150 consecutive newly diagnosed acute myelogenous leukemia (AML) patients at St. Jude Children's Research H ospital, and 10 were cases referred to the National Institute of Cance r in Rio de Janeiro, Brazil. There were 5 Down syndrome patients and o ne patient with chronic myeloid leukemia (Ph+) in blastic crisis. Twel ve patients had significant hepatosplenomegaly. Leukemic cell morpholo gy and cytochemistry were consistent with the M7 classification in 17 cases, and all cases tested expressed megakaryocytic surface antigens. AMKL patients were significantly younger than other AML patients (P = 0.0001) and had poorer responses to therapy (P = 0.03, univariate ana lysis only). Ten of 24 failed induction, and only 5 are disease-free a t 6 months to 4.5+ years. We conclude that AMKL usually affects young children, frequently producing marked organomegaly. It comprises appro ximately 10% of pediatric AML cases, and responds poorly to intensive AML therapies.