CD20-negative diffuse large B cell lymphoma: a comprehensive analysis of 695 cases.

CD20 expression is absent in a variety of diffuse large B cell lymphomas (DLBCLs), including plasmablastic lymphoma, primary effusion lymphoma, anaplastic lymphoma, kinase-positive DLBCL, and large B cell lymphoma arising in human herpesvirus 8-associated multicentric Castleman disease. These rare and heterogeneous tumors are characterized by the presence of proliferating immunoblasts with similar transcriptional profiles as those of plasma cells and are typically associated with highly aggressive pathologies, with high levels of chemotherapy resistance and low survival rates; thus, they pose significant diagnostic and treatment challenges. We conducted a systematic literature review of the limited existing clinical data to summarize the current knowledge regarding the biological basis, diagnostic limits, and potential therapeutic targets of distinct variants of CD20-negative DLBCL. This review will hopefully increase the awareness of these rare disorders among clinicians and pathologists and prompt basic and clinical research.