INTERPHASE FLUORESCENCE IN-SITU HYBRIDIZATION (FISH) AS A POWERFUL TOOL FOR THE DETECTION OF ANEUPLOIDY IN MULTIPLE-MYELOMA

Conventional cytogenetic (CC) studies performed in multiple myeloma (M M) are difficult because of the low proliferation rate of plasma cells (PC). The purpose of this study was to compare results obtained by CC and by FISH for the detection of numeric chromosomal changes in patie nts with MM. PC DNA content, CC and interphase FISH analysis were perf ormed on 29 consecutive patients with MM. Fifteen patients (control gr oup) had known cytogenetic abnormalities identified by CC. The other 1 4 patients (study group) had a normal karyotype but an abnormal DNA co ntent. Bone marrow material prepared for CC or cytospin slides were pr obed with classical satellite III or alpha satellite DNA sequences for chromosomes 3, 7, 8, 9, 11 and 15 (chromosomes 3, 7, 9, 11, 15 probes for hyperdiploid patients and the chromosome 8 probe for hypodiploid patients). In the control group, an unexplained discrepancy between CC and FISH occurred for only one chromosome in one patient. Also in thi s group, four patients had only one abnormal cell by CC and the numeri c changes in these patients were always confirmed by FISH analysis. In the study group, FISH analysis showed an abnormal result in all but o ne patient. From these data, we conclude that FISH improves the detect ion of cytogenetic abnormalities in multiple myeloma. Using commercial ly available DNA probes for the most frequent numeric changes and slid es for CC or cytospin slides, we demonstrated abnormal cytogenetics by FISH in 28/29 patients. In further studies, use of FISH could permit a more accurate description of numeric changes and their prognostic va lue in MM as well as an approach to clonal evolution. It would also be of interest in the study of monoclonal gammopathies of undetermined s ignificance.