Detection of M-bcr/abl fusion by fluorescence in situ hybridization (FISH) in a case of Ph negative CML

A balanced reciprocal translocation, t(6;9)(p21;q34), was identified in a female patient diagnosed with chronic myeloid leukemia (CML). Both homologs of chromosome 22 were of normal length and morphology. Southern blotting revealed a bcr rearrangement with BglII and HindIII. Two signals for the abl probe were demonstrated by fluorescence in situ hybridization (FISH), one on the normal chromosome 9 and the second on a chromosome 22. Thus, molecular rearrangement of bcr resulted from insertion of an abl gene within the bcr region despite absence of a Ph chromosome.