A unique cytogenetic abnormality, t(2;7)(p13.1;p21.3), in a Philadelphia-positive chronic myeloid leukemia

The Philadelphia (Ph) chromosome is present in more than 90% of patients suffering from chronic myeloid leukemia (CML). It is the product of a reciprocal translocation between the long arms of chromosomes 9 and 22, resulting in the transfer of the 3' portion of the proto-oncogene ABL from 9q34 to the 5' portion of the breakpoint cluster region (BCR) on 22q11. Currently, most CML cases are treated with Imatinib and variant rearrangements are thought to have no specific prognostic significance, although the events of therapy resistance have not yet been studied. In this study we report a novel case of CML exhibiting an uncommon t(2;7)(p13.1;p21.3) besides t(9;22)(q34;q11). This unusual translocation has been characterized by fluorescence in situ hybridization (FISH) and array-proven multicolor banding (aMCB), the latter being extremely significant in characterizing breakpoint regions in detail. The underlying mechanisms and prognostic implications of this cytogenetic abnormality are discussed in this study.