Chromosome 13 abnormalities in multiple myeloma are mostly monosomy 13.

Chromosome 13 abnormalities are frequently observed in multiple myeloma (MM). Several reports recently demonstrated the strong prognostic value of these abnormalities, associated with a short survival. Cytogenetic studies have shown that most of these abnormalities are complete monosomies. In order to define the common minimal deletion, we analysed a series of 234 patients with MM using fluorescence in situ hybridization (FISH) with a panel of five probes mapping along the whole chromosome 13. A chromosome 13 abnormality was observed in 98 patients (42%), 90 of whom (92%) displayed a complete monosomy. In seven of the eight remaining patients presenting partial deletions, the three probes specific for the 13q14 region were deleted. Only one patient (1%) displayed a small deletion of the D13S319 locus. In conclusion, FISH should be used for the analysis of chromosome 13 abnormalities, using probes mapping in the 13q14 region.