Duplication of the der(13)t(12;13)(p13;q14) in chronic myelomonocytic leukemia

A case of chronic myelomonocytic leukemia with a reciprocal translocation (12;13)(p13;q14) and other numerical and structural abnormalities is described. Most of the metaphases examined showed duplication of the der(13)t(12;13), leading to trisomy of the translocated segment of chromosome 12. Using fluorescence in situ hybridization we observed that the breakpoint on chromosome 13 is centromeric to the retinoblastoma gene. Since other cases with apparently similar t(12;13) have recently been reported, we conclude that this structural rearrangement may be a rare but non random event in hematologic disorders.