Leukemic transformation with trisomy 8 in essential thrombocythemia: a report of four cases

Karyotype analysis of bone marrow samples was performed in 20 cases of essential thrombocythemia (ET) at the time of diagnosis. Three patients had karyotype abnormalities at the time of diagnosis; trisomy 8, deletion of Y, and del(9)(q?) in each. The patient who had trisomy 8 at the time of diagnosis underwent myeloid blastic transformation in 35 months. Three patients whose karyotypes were normal at the time of diagnosis developed a chromosome abnormality with trisomy 8 when they developed myeloid blastic transformation 38, 79 and 86 months after initial diagnosis of ET. Two patients with blastic transformation had been treated with busulfan, one with hydroxyurea and one with methyl-6-[3-(2-chloroethyl)-3-nitorosoureidol]-6-deoxy-alpha-D-glucopyranoside (MCNU). It is suggested that progression of the disease may have increased the incidence of trisomy 8 and the development of leukemic transformation.