OBJECTIVETo investigate the value of multiplex fluorescence in situ hybridization (M-FISH) for the detection of complex chromosomal abnormalities (CCA) of chronic myeloid leukemia in blast crisis (CML-BC).

METHODSM-FISH was used to study 26 cases of CML-BC with CCA assayed by conventional cytogenetics (CC).

RESULTSSixty-nine kinds of structural rearrangements were detected by M-FISH besides typical t (9;22) translocation, among them only 10 were balanced ones and 59 unbalanced ones including 1 insertion, 6 deletions, 52 translocations and derivative chromosomes. In addition, 23 numerical abnormalities were detected. All chromosomes were involved in CML-BC, and chromosomes 17, 2, 8, 16 involvements were the most frequent. M-FISH failed to find out the abnormal clone in 1 case, discovered CCA clones that were missed CC in 6 cases. Clarified 16 kinds of aberrations which could not be identified CC and corrected 5 aberrations made wrong description by CC. Thirty-five kinds of translocations were found by M-FISH which were missed by CC. The aberrations of der (9) t (16; 6; 9; 22) and der (18) t (16; 18; 19) we found were reported in the literature for the first time.

CONCLUSIONSM-FISH can refine CCA in CML-BC, find out or correct the missed or misidentified abnormalities by CC. The frequent secondary chromosomal abnormalities in CML-BC with CCA are different from that in CML.