Biallelic BCL6 rearrangements by dual t(3;14)(q27;q32) and t(3;22)(q27;q11) translocations in diffuse large B-cell lymphoma.

3q27 chromosomal translocation involving the BCL6 gene is one of the most frequent forms of cytogenetic abnormality observed in B-cell lymphoma. We report a case with diffuse large B-cell lymphoma (DLBCL) presenting dual 3q27 translocations. The patient was a 71-year-old man who presented with swelling of multiple abdominal lymph nodes (LNs) and obstructive jaundice. LN biopsy exhibited dense proliferation of atypical large cells expressing CD20, MUM1/IRF4, BCL2, BCL6, and MYC, but not CD10. He was diagnosed with non-GCB/ABC type DLBCL and showed an initially good response to R-CHOP chemotherapy, but relapsed soon after the completion of therapy. Chromosomal analysis of the biopsied LN exhibited multiple abnormalities including t(3;14)(q27;q32) and t(3;22)(q27;q11). Fluorescence in situ hybridization (FISH) using BCL6 break-apart probes confirmed chromosomal breaks occurring on both BCL6 alleles. Molecular analysis revealed two independent rearrangements of BCL6, either with the IGH or the IGL gene. 3q27 breakpoints were located 1.2kb apart from each other within the first intron of BCL6, while the IGH and IGL breaks occurred at the 5' of IGHG2 and within IGLV3-1, respectively. The results suggest that biallelic BCL6 rearrangements might be a rare but recurrent genetic event in B-cell lymphoma.