Complex karyotype and N-RAS point mutation in a case of acute megakaryoblastic leukemia (M7) following a myelodysplastic syndrome

The development of acute megakaryoblastic leukemia (ANLL-M7) following myel odysplastic syndrome (MDS) has been described only in a few reports, and th e mutations necessary for this transformation are still unknown. In this st udy, we describe a case of ANLL-M7 with a previous history of MDS presentin g a complex karyotype 46,XX, t(4;11)(q21;q23),del(5)(q13q33), t(12;13)(p13; q21) and N-RAS point mutation. During MDS, the patient showed a hypercellul ar myelogram with dysplasia of the three myeloid lineages and the clinical symptoms characteristic of the 5q- syndrome. During the follow-up, we obser ved the appearance of two additional subclones, one with an isochromosome 1 7q and another with polyploidy. The presence of an isochromosome 17q in one subclone and polyploidy in another is probably due to the genetic instabil ity generated by the malignant transformation. (C) Elsevier Science Inc., 2 000. All rights reserved.