EBV Positive Diffuse Large B Cell Lymphoma with Negative Pan-B Cell Markers, Case Report, and Literature Review.

Most B cell lymphomas are positive for one or more B cell markers including CD19, CD20, CD79a, or PAX5. However, rare cases of mature B cell lymphoma not expressing any B cell markers have been characterized and recognized as distinct diagnostic entities by current classification guidelines, including plasmablastic lymphoma, primary effusion lymphoma, and ALK-positive large B cell lymphoma. We present a case of pan-B cell marker negative, EBV positive diffuse large B cell lymphoma that is positive for OCT2, BOB1, and clonal immunoglobulin gene rearrangement that does not meet diagnostic criteria for any B cell lymphoma by current 4^th and 5^th Ed beta version WHO Hematolymphoid Tumors classification. In challenging cases like the one presented, utilizing OCT2 and BOB1 immunohistochemical stains can assist in determining B cell lineage. The WHO tumor classification system should consider adding OCT2 and BOB1 as alternative B cell lineage markers into their corresponding categories.