Chromosome 13 abnormalities are frequently observed in multiple myeloma (MM
). Several reports recently demonstrated the strong prognostic value of the
se abnormalities, associated with a short survival. Cytogenetic studies hav
e 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 fi
ve probes mapping along the whole chromosome 13, A chromosome 13 abnormalit
y was observed in 98 patients (42%), 90 of whom (92%) displayed a complete
monosomy. In seven of the eight remaining patients presenting partial delet
ions, the three probes specific for the 13q14 region were deleted, Only one
patient (1%) displayed a small deletion of the D13S319 locus. In conclusio
n, FISH should be used for the analysis of chromosome 13 abnormalities, usi
ng probes mapping in the 13q14 region.