Two-step development of t(14;18)(q32;q21) followed by t(3;14)(q27;q32) involving the same IGH allele to generate t(3;14;18)(q27;q32;q21) in follicular lymphoma, grade 3A

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We herein described a female patient in her 60s with metastatic breast cancer who concomitantly developed stage IV follicular lymphoma (FL). Lymph node biopsy revealed FL grade 3A histopathology. Lymphoma cells were positive for CD10, CD20, CD79a, BCL2, and BCL6 and negative for CD3. G-banding and fluorescence in situ hybridization showed a major cytogenetic clone marked with t(14;18)(q32;q21)/IGH::BCL2 and a minor clone with a 3-break translocation, t(3;14;18)(q27;q32;q21), involving BCL6, IGH, and BCL2. We amplified the DNA fragments encompassing the BCL2::IGH and BCL6::IGH junctions by a long-distance polymerase chain reaction and found that the former fragment comprised sequences of the far 3′ major breakpoint region cluster of BCL2 followed by IGHJ6 and those of IGHG1, while the latter fragment comprised sequences of the major translocation cluster of BCL6 and those of IGHG2. In der(3)t(3;14;18), the coding exons of BCL2 and BCL6 aligned in the same transcriptional orientation and the intronic Eμ enhancer of IGH was present between the two genes. We proposed that t(3;14;18) was generated by two-step translocations and BCL2::IGH and BCL6::IGH involved the same IGH allele.

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