Cytotoxic Epstein–Barr virus-positive large B cell lymphoma: a regulatory B cell-derived neoplasia?

Aims: A new subtype of granzyme B (GrB)-producing regulatory B cells (Bregs) has been described recently; these peculiar cytotoxic B cells are increased significantly in interleukin (IL)-21-rich settings, and in particular during HIV and Epstein–Barr virus (EBV) infection. Our aim is to report a unique case of an EBV-positive diffuse large B cell lymphoma (DLBCL) with cytotoxic features arisen in an HIV+ patient, and to understand if this lesion may represent a proliferation of neoplastic cytotoxic Bregs. Methods and results: We describe a 66-year-old male patient who presented with cervical lymph node enlargement and B symptoms; subsequently, HIV infection was diagnosed. Histopathological, immunohistochemical and molecular studies were performed, and revealed an EBV-positive DLBCL with cytotoxic features. Considering the immunological setting and unconventional phenotype observed, we tried to evaluate further the expression of GrB and IL-21 in another 150 aggressive B cell lymphomas (17 of 150 EBV+, two of 150 EBV+/HIV+). Minimal dot-like expression of GrB was found in seven lymphomas (in fewer than 1% of tumour cells), three of which were EBV-positive. Conclusions: Breg origin has never been reported in B cell lymphomas. We describe an exceptional case of EBV-positive DLBCL with aberrant expression of cytotoxic markers in a patient with a previously unknown HIV infection. We propose cytotoxic Bregs as a possible normal counterpart for this unusual tumour.