Plasmablastic lymphoma in an elderly immunocompetent patient.

Plasmablastic lymphoma (PBL) is a distinct type of diffuse B cell lymphoma that typically occurs in the oral cavity of patients with HIV infection or immunodeficiency status. PBL is characterized by its plasmablastic morphology and an immunophenotype indicative of a plasma cell differentiation. We present a case of a 75-year-old HIV-negative and Epstein-Barr virus (EBV)-negative patient presenting with an isolated oral cavity mass. The tumor consisted of a monotonous proliferation of undifferentiated large cells with relatively abundant cytoplasm, eccentrically located round nuclei with prominent nucleoli and numerous mitoses. Immunohistochemically, these cells were negative for CD45 and B cell antigens, while they showed diffuse positivity of CD138 and focal staining for epithelial membrane antigen (EMA), indicating plasma cell differentiation. Based on these histopathological and immunohistochemical characteristics, we diagnosed it as PBL. The patient received chemotherapy and is alive with locally persistent disease 3 years after diagnosis. To date, only several cases of oral PBL have been reported in HIV-negative, EBV-negative and immunocompetent patients. PBL should be included in the differential diagnosis of oral mass lesions and careful evaluation of the morphology and awareness of the existence of this uncommon type of lymphoma can lead to a correct diagnosis.