Acute megakaryoblastic leukemia in an infant with a novel t(1;9)(p32;q34)

We report a case of a 14-month-old girl with acute megakaryoblastic leukemi a (AMKL). May-Giemsa staining of the bone marrow cells revealed the prolife ration of two distinct types of blasts. One type of blasts had cytoplasmic blebs, and the other showed a lymphoblastic morphology without blebs. Both types of blasts were negative for peroxidase and esterase reactions. Electr on microscopic platelet peroxidase (PPO) reaction also revealed the presenc e of two types of blasts. One had irregular-shaped nuclei and positive PPO reaction in the nuclear envelope and rough endoplasmic reticulum but not in the Golgi apparatus. These types of blasts were considered to be megakaryo blasts. The other had an immature phenotype with round nuclei and positive PPO reaction in the nuclear envelope, rough endoplasmic reticulum, and the Golgi apparatus. The origin of this type of blasts could not be defined by their morphology. Surface marker analysis indicated that most of the leukem ic cells expressed platelet markers, gpIIb, gpIIb/IIIa gpIX, and gpIb alpha . Karyotypic analysis of the bone marrow cells of this unique subset of AMK L demonstrated a novel translocation, t(1;9)(p32;q34). (C) 2000 Elsevier Sc ience Inc. All rights reserved.