Recurrent involvement of heterochromatic regions in multiple myeloma-a multicolor FISH study.

Chromosome aberrations are important prognostic markers in multiple myeloma (MM), but their identification may be hampered by complexity of the karyotypes. Using multicolor fluorescence in situ hybridization (mFISH), we found cryptic aberrations in 7 of 10 patients with a complex karyotype. Moreover, in addition to typical aberrations involving 1q, 13q, 14q and 17p and structural aberrations in chromosomes 1, 6, 9 and 19, (iso)dicentric chromosomes and whole-arm translocations were detected. These chromosome aberrations were generated by breaks in heterochromatic regions indicating an increased breakage of these regions, which may predispose to the generation of chromosome aberrations in multiple myeloma.