Chromosome aberrations in a series of 120 multiple myeloma cases with abnormal karyotypes

Abstract

We identified 120 multiple myeloma (MM) cases with satisfactory cytogenetic evaluation and abnormal karyotypes. Hyperdiploid karyotype was found in 77 cases (64%), hypodiploid in 30 cases (25%), and the remaining 13 cases (11%) had a pseudodiploid karyotype. The most common numerical abnormalities were gains of chromosomes 15, 9, 3 followed by chromosomes 19, 11, 7, 21, and 5. Whole chromosome losses were also frequent involving primarily chromosomes X/Y, 8, 13, 14, and 22. Most cases showed also structural rearrangements leading to del(1p), dup(1q), del(5q), del(6q), del(8p), del(9p), del(13q), and del(17p). Chromosome 13/13q deletion was found in 52% of cases; complete loss of 13 was observed in 73% of cases, whereas 27% had interstitial deletions. In addition, 13/13q deletions occurred in 75% of nonhyperdiploid myeloma but only 39% of the hyperdiploid had 13/13q deletions. Translocations affecting 14q32/IGH region was seen 40 cases; t(11;14)(q13;q32) in 17 cases, t(14;16)(q32;q23) and t(8;14)(q24;q32) in three cases each, and t(6;14)(p21;q32) and t(1;14)(q21;q32) in two cases each. The remaining 14q32 translocations had various t(V;14) partners or of an undetermined origin. Remarkably, the 14q32/IGH translocations were less frequent in the hyperdiploid karyotypes than the nonhyperdiploid karyotypes (17 vs. 63%). Fourteen cases showed break at 8q24/CMYC site; seven of those had Burkitt's-type translocations. Our results revealed that conventional cytogenetics remains an important tool in elucidating the complex and divers genetic anomalies of MM. Cytogenetics identifies two distinct groups of MM, hyperdiploid and nonhyperdiploid, and establishes the presence of prognostic chromosomal markers such as 13/13q, 17p, 8q24, and 16q aberrations.