Polysomy 13 with concomitant deletion of 13q13-14 involving the retinoblastoma gene and the D13S25 locus in a case of acute myeloid leukemia

We herein describe a case of acute myeloblastic leukemia (AML), FAB subtype M4, with an unfavorable clinical course and a complex karyotype, including 4-9 copies of chromosome 13. Polysomy 13 was a result of clonal evolution. Fluorescence in situ hybridization (FISH) revealed a cytogenetically unrec ognizable deletion within 13q13-14 that included the retinoblastoma gene (R B) and the D13S25 locus in all but one copy of chromosome 13. The only chro mosome 13 that did not show a deletion affecting the q13-14 region was tran slocated to chromosome 7, resulting in a dic(7;13)(q21;p11). In this case, the coexistence of polysomy and a partial deletion within the same chromoso me point toward a possible formation of a fusion product with oncogenic pot ential and its consecutive amplification as a critical alteration in this c ase. (C) 2000 Elsevier Science Inc. All rights reserved.