Conventional Cytogenetics and Interphase Fluorescence In Situ Hybridization Results in Multiple Myeloma: A Turkey Laboratory Analysis of 381 Cases

Abstract

Multiple myeloma (MM) is an uncontrolled proliferation of plasma cells and these cells play an important role in the immune system. In this research, we retrospectively analyzed cytogenetic abnormalities in 381 patients with MM. Conventional cytogenetic analysis was successful in 354 patients (92.9%). Chromosomal abnormalities were detected in 31.9% (113/354) and 45.8% (116/253) of patients screened with conventional cytogenetics and FISH, respectively. Of 113 patients with chromosomal abnormalities, 31 patients (27.4%) had hyperdiploid and 26 of 31 patients with hyperdiploidy had both numerical and structural anomalies. On the other hand, non-hyperdiploidy was observed in 62 patients (54.8%). The most common gains of chromosomes were 15, 9, 19 followed by 3, 5, 11, and 21. Whole chromosome losses were also frequent involving Y, 13 and 22 chromosomes. In our patients, 1q gain was determined in a total of 25 patients (22%), including 7 structural abnormalities and 19 unbalanced translocations causing complete or partial duplication of the long arm of chromosome 1. Although the breakpoints were different, t(1;5) balanced translocation and unbalanced translocations of t(1;2), t(1;3), t(1;7), t(1;16) and t(1;19) were observed twice. The most common structural abnormality was the deletion of the short arm of chromosome 13 (13q) or monosomy of chromosome 13 (-13) (24.1%, 61/253) in patients evaluated by FISH. Deletion involving chromosome 17p (del 17p) or monosomy of chromosome 17 (-17) were found in 31 (12.3%) patients. Translocations involving IgH regions were as follows: t(11;14)(q13;q32.33) in 22 (8.7%), t(4;14)(p16.3;q32.33) in 22 (8.7%) and t(14;16)(q32.33;q23.1) in 2 (0.8%) patients. In addition, t(14;17)(q32;q21) translocation was detected in a multiple myeloma patient for the first time in this study. There are a limited number of large study groups including both cytogenetic and FISH findings in MM patients. As the number of these studies increases, it is thought that new cytogenetic data can be guiding especially in clinical risk determination.

Keywords: Chromosomal abnormalities; Cytogenetics; FISH; Multiple myeloma.

Fig. 1

Distribution of chromosome abnormalities in MM patients. a A pie chart showing the percentage of numerical and structural abnormalities in the total of 113 MM patients. b A bar graph showing the comparison of numerical and structural abnormalities in the four ploidy groups

Fig. 2

Frequency of chromosomal gains and losses in 113 multiple myeloma patients

Fig. 3

Representative examples of 1q gains