Cytogenetic Abnormalities in Histologically Confirmed Multiple Myeloma.

In multiple myeloma, conventional cytogenetics is limited by low proliferation activity of plasma cells in culture. Despite that, nonrandom chromosomal abnormalities have been reported in one third of cases. Recently, the karyotype has emerged as an important prognostic factor in multiple myeloma. In this study, we identified 104 histologically confirmed multiple myeloma cases with satisfactory cytogenetic evaluation and abnormal karyotype. FISH analysis was used to evaluate certain chromosome abnormalities or to monitor treatment response. Hyperdiploid karyotype was found in 67 cases (64%), hypodiploid in 25 cases (24%), and the remaining 12 cases (12%) had a pseudodiploid karyotype. The most common numerical abnormalities were gains of chromosomes 9, 15, 3 followed by chromosomes 19, 21, 11, 7, and 5. Whole chromosome losses were also frequent involving primarily chromosomes 13, 8, 14, 22, and 16. In the hypodiploid cases, loss of chromosome 13 was more evident, seen in 19/25 (76%) cases. Most cases showed also structural rearrangements leading to del(1p), dup(1q), del(6q), del(9p), del(13q), del(17p), del(8p), 3p/3q abnormalities, and 11p/11q abnormalities. Translocations affecting 14q32/IGH region was the most frequent seen 36 times in 34/104 (33%) cases; t(11;14)(q13;q32) in 13 cases, t(1;14), t(6;14), and t(8;14) in 2 cases each, and the remaining cases had various t(V;14) partners or of an undetermined origin. The 14q32/IGH translocations were less frequent in the hyperdiploid karyotypes than the hypodiploid and pseudodiploid karyotypes (18% vs 60%). Nine cases showed break at 8q24/CMYC site; six of those had Burkitt’s-type translocations. Other non-random translocation was t(1;16) seen in three cases. Coventional cytogenetic remains an important tool in elucidating the complex and diverse genetic anomalies of multiple myeloma. Acccordingly well defined cytogenetic subgroups can be identified. At the present time, FISH and other molecular genetic techniques are important adjuncts, but should not be a substitute for conventional karyotyping. The clinical and hematological correlates of the karyotype in our series is being evaluated.