Detection of chromosome 13q deletions and IgH translocations in patients with multiple myeloma by FISH: Comparison with karyotype analysis

Multiple myeloma ( MM) is a plasma cell dyscrasia characterized by frequent 13q deletions and IgH translocations that have clinical prognostic significance. We evaluated clonal plasma cells by interphase fluorescence in situ hybridization ( FISH) and combined with immuno fluorescence detection of cytoplasmic light chain (cIg-FISH) for the presence of 13q deletions and IgH translocations. The FISH results were compared with conventional cytogenetic analysis. Of the 25 bone marrow specimens from MM patients, 11 (44%) had 13q deletions. IgH translocations involving cyclin D1 (t(11; 14)) and FGFR3 ( t( 4; 14)) were found in 32 and 36%, respectively. P53 deletions were detected in 20% of the cases. One patient had coexistence of t( 11; 14) and t( 4; 14), which has not been previously reported. Conventional cytogenetic analysis was performed in 15 cases and revealed complex numerical and structural changes in 7. Karyotype analysis failed to detect 3 of 6 cases with 13q deletions, and also missed most of the IgH translocations and p53 deletions detected by cIg-FISH. On the other hand, the complex numerical and structural changes shown by conventional cytogenetics were not demonstrated by interphase FISH. Since 13q deletions, IgH translocations and a hypodiploid karyotype are significant prognostic factors for MM, our study illustrates the importance of combining conventional cytogenetics with interphase FISH analysis in patients with MM.