Translocation (3;16)(q27;p11) in a patient with diffuse large B-cell lymphoma associated with the BCL-6 gene rearrangement

The gene for interleukin-21 receptor is the partner of BCL6 in t(3;16)(q27;p11), which is recurrently observed in diffuse large B-cell lymphoma

BCL6 translocation affecting the chromosomal band 3q27 can involve a number of non-immunoglobulin (non-IG) gene loci as partners. We report here that the gene for interleukin-21 receptor (IL-21R) is the partner of BCL6 in t(3;16)(q27;p11) translocation. The two breakpoints on 16p11 of a lymphoma cell line YM and case no. 1012 with diffuse large B-cell lymphoma, both of which carried t(3;16), were localized within the 27-kb intron 1 of IL-21R. As a result of t(3;16), the promoter region of IL-21R was substituted for the regulatory sequences of BCL6 in the same transcriptional orientation. Reverse transcriptase-mediated polymerase chain reaction revealed chimeric mRNA consisting of two non-coding exons 1a/1b of IL-21R and coding exons of BCL6 in both lymphoma cells. Fluorescence in situ chromosomal hybridization of YM metaphase cells revealed fusion signals that contained both the BCL6 and IL-21R sequences on the der(3)t(3;16) chromosome. IL-21R was actively transcribed in YM cells, while BCL6 that was under the control of the IL-21R promoter was only moderately expressed at the mRNA and protein level. We constructed expression plasmid of BCL6 that followed the promoter sequences of IL-21R. COS-7 cells transiently transfected with the plasmid expressed high level Bcl-6 protein and displayed nuclear staining with a characteristic punctate pattern by immunofluorescence, indicating that expression of BCL6 can be enhanced by t(3;16). This study added to the list of non-IG partners of BCL6 translocations a new class of gene, i.e. cytokine receptor gene, the expression of which is closely associated with lymphoid cells.

Blastic natural killer cell lymphoma arising from the mediastinum with terminal deoxynucleotidyl transferase expression

Blastic natural killer (NK) cell lymphoma/leukemia is a relatively rare NK cell malignancy. We report the second case of blastic NK cell lymphoma arising from the mediastinum with an aggressive clinical course. The patient was a 63-year-old Japanese man with an anterior mediastinum tumor. The biopsy specimen showed diffuse proliferation of tumor cells with frequent mitotic figures and apoptotic bodies. Both angiocentric features and small foci of coagulative necrosis were found in this section. The tumor cells had medium to large nuclei with a fine chromatin pattern, inconspicuous nucleoli and scanty cytoplasm. The nuclear contour was oval to moderately irregular, showing slight pleomorphism as compared with typical lymphoblastic lymphoma. The tumor cells were positive for CD2, CD56 and terminal deoxynucleotidyl transferase, but negative for other T-cell antigens, B-cell antigens and myeloid markers. In situ hybridization for Epstein-Barr virus encoded small ribonucleic acid 1 was negative.