Plasmablastic lymphoma involving the parotid gland.

Plasmablastic lymphoma is a rare form of non-Hodgkin lymphoma. It is strongly associated with HIV infection, although it has been recognized in immunocompetent patients. Plasmablastic lymphoma has a predilection for the oral cavity. Its occurrence in the parotid gland has not been previously described. We report a case of an HIV positive man who developed a rapidly enlarging parotid mass. A core biopsy of the parotid mass was evaluated by routine microscopy, immunohistochemistry, and in situ hybridization. The tumor was comprised of sheets of large cells with abundant cytoplasm, eccentric nuclei and prominent nucleoli. The cells exhibited a plasmacytic immunophenotype including expression for CD38 and CD138. An in situ hybridization assay for Epstein-Barr virus was positive. These findings were diagnostic of plasmablastic lymphoma. Plasmablastic lymphoma is notoriously difficult to diagnose, particularly when it arises in unexpected sites outside of the oral cavity. As an aggressive lymphoma, plasmablastic lymphoma must be considered in the differential diagnosis of a high-grade malignant neoplasm not just in the oral cavity but at non-oral sites including the parotid gland, particularly in an HIV-positive individual.