A rare type of primary CD19-negative diffuse large B-cell lymphoma presenting as an infraorbital mass in the maxillary sinus

A 38-year-old male recently diagnosed with acute on chronic rhinosinusitis and orbital cellulitis presented with a right painful infraorbital mass and swelling. Fine needle aspiration of the mass demonstrated atypical lymphoid infiltrate highly suggestive of lymphoma. Flow cytometry and immunophenotypic analysis detected an abnormal lymphocytic population characterized by positive CD20, CD38, and CD10, however, the CD19 marker was negative. Whole-body positron emission tomography showed a sizeable hypermetabolic mass centered at the right maxillary sinus, extending into the right orbit, and several hypermetabolic lymph nodes in the right neck. A diagnosis of high-grade CD19-negative DLBCL was made and the patient was initiated on R-HyperCVAD (Rituximab- cyclophosphamide, vincristine, Adriamycin, dexamethasone) chemotherapy protocol. The diagnosis of paranasal lymphoma may remain elusive for months leading to delays in treatment, thus a high index of suspicion is warranted. The loss of CD19 expression in DLBCL represents a diagnostic challenge because this surface marker is widely used to gate the B cells for immunophenotyping and flow cytometry analysis. It also leads to therapeutic limitations to CD19 targeting therapies.