Characterization of Patients with Multiple Myeloma and t(4;14) Detected by Fluorescence In Situ Hybridization.

Multiple myeloma (MM) is a genetically unstable malignancy of postgerminal center B-cells. Almost 40% of intramedullary MM tumors show primary translocations that affect immunoglobulin heavy chain (IgH) gene. These include t(4;14)(p16;q32) which results in the dysregulated expression of two potential oncogenes, MMSET on der(4) and FGFR3 on der(14), and has been associated with poor outcome. The main goals of this study were to determine the incidence and clinical significance of t(4;14) among our MM patients. Therefore, we studied bone marrow specimens from 65 patients with MM by fluorescence in situ hybridization (FISH). All cases were screened for IgH rearrangements, t(4;14), t(11;14), and 13q14 deletions using the locus-specific probes LSI IgH dual color, break apart, LSI IGH/FGFR3, LSI IGH/CCND1, and LSI D13S319 (Vysis). FISH analysis revealed 35 cases (54%) involving IgH locus. 8 patients (12.3%) had a t(4;14), and 13 cases (20%) showed a t(11;14). In the remaining 14 samples (21.5%), IgH rearrangements were observed, but the translocation partner was not one of the loci for we tested. Furthermore, 13q14 deletions were more frequent among patients with t(4;14) than among those with t(11;14) (62.5% vs 30.7% respectively, p=0.03). Regarding clinical parameters, presence of t(4;14) was significantly associated with anemia (mean value: 9.0 g/dl, p=0.049), elevated LDH levels (mean value: 535.4 U/l, p=0.05), Durie III stage (p=0.049), and number of lytic bone lesions >2 (p=0.007). Finally, the survival median of patients with t(4;14) was 23 months vs 48 months for the group without this abnormality. Cases with t(11;14) did not show adverse correlation with survival.

Based on these data, FISH is a successful technique to detect translocations affecting telomeric localization of both chromosomal partner loci. In addition, we confirmed t(4;14) as an important factor of poor prognostic in MM. Its detection is essential to lead a correct evaluation of patients at diagnosis.