Fluorescence in situ hybridization characterization of different cryptic BCR-ABL rearrangements in chronic myeloid leukemia.

Using fluorescence in situ hybridization probes, obtained from bacterial artificial chromosome (BAC) libraries that relate to sequences either side of the BCR and ABL genes, this study characterized four chronic myeloid leukemia cases with cryptic BCR-ABL rearrangements. Each case showed evidence of a different underlying mechanism: one case showed a microinsertion of BCR into ABL, another a microinsertion of ABL into BCR, and the third showed a complex rearrangement including deletion of adjacent flanking sequences, consistent with the reverse translocation model of cryptic rearrangement. The fourth case also showed evidence of a more complex rearrangement involving chromosome 1.