Two cases of diffuse large B-cell lymphoma/high-grade B-cell lymphoma carrying t(3;8)(q27;q24)/<i>BCL6</i>::<i>MYC</i>

We describe two patients with diffuse large B-cell lymphoma (DLBCL)/high-grade B-cell lymphoma (HGBL) that carried t(3;8)(q27;q24)/BCL6::MYC. In case 1, the patient was an 82-year-old man who presented with widespread bone marrow (BM) involvement and leukemic manifestation. Lymphoma cells in BM and peripheral blood were composed of not only large cells but also small cells, and those in the lymph node (LN) biopsy exhibited the germinal center B-cell (GCB) phenotype and carried t(14;18)(q32;q21), suggesting transformation of previously low-grade follicular lymphoma. In case 2, the patient was a 55-year-old man who presented with generalized lymphadenopathy and M protein in serum. Lymphoma cells exhibited the non-GCB/activated B-cell phenotype and included plasma cell-stage cells that expressed CD38 at high levels, indicating that lymphoma cells originated from mature B-cells that had exited GC to secrete immunoglobulins. G-banding revealed a subtle difference between chromosome 3 and 8 homologues in both cases, and fluorescence in situ hybridization revealed co-localization of 3′ BCL6 and 3′ MYC signals at the telomeric end of der(3) and that of 5′ MYC and 5′ BCL6 signals at the telomeric end of der(8), confirming BCL6::MYC gene fusion. The case 1 patient died soon after of disease progression, while the case 2 patient survived for 3 years and 6 months following the initial treatment. LN biopsies in both cases revealed DLBCL/HGBL histopathology with a high Ki-67 proliferation index and MYC expression in 90% of lymphoma cells; however, t(3;8)(q27;q24)/BCL6::MYC may not be regarded as “true” MYC/BCL6 double-hit.