Various patterns of IgH deletion identified by FISH using combined IgH and IgH/CCND1 probes in multiple myeloma and chronic lymphocytic leukemia

Introduction: Interphase fluorescence in situ hybridization (FISH) can identify submicroscopic deletions adjacent to the breakpoints of rearrangements undetected by conventional cytogenetics. In this study, the characteristics and frequency of the IgH deletion identified by interphase FISH were investigated in patients with multiple myeloma (MM) and chronic lymphocytic leukemia (CLL). Methods: The study group included 29 patients with MM and eight patients with CLL. Interphase FISH was performed with the IgH dual color, break-apart rearrangement probe and the IgH/CCND1 dual color, dual fusion translocation probe. Results: The IgH deletion was found in 14% (4/29) of patients with MM and 13% (1/8) of the patients with CLL. Four patients had deletions of the whole or variable region of IgH on the native chromosome 14, whereas one patient had a deletion of the IgH variable region on a der(11)t(11;14). In two patients, the IgH break-apart FISH showed both patterns with and without IgH deletions. In cases showing the same pattern by IgH break-apart FISH, the IgH/CCND1 FISH showed different patterns, and vice versa. Conclusion: A variety of patterns of the IgH deletion were identified by interphase FISH using IgH break-apart and IgH/CCND1 probes in patients with MM and CLL. The results of this study suggest that the integrated information obtained with IgH break-apart and IgH/CCND1 FISH was needed to interpret FISH results unambiguously.