Extramedullary plasmacytoma of the sublingual gland

Extramedullary plasmacytoma originating from the sublingual gland is an extremely rare phenomenon. The authors report a case of extramedullary plasmacytoma of the sublingual gland. A 75-year-old man presented with complaints of a painless mass on his floor of the mouth. On physical examination, a submucosal nodule, measuring approximately 30 mm × 10 mm, was observed on the left floor of the mouth, for which the patient underwent mucosal resection. Histopathological features included a dense monoclonal infiltrate of plasma cells with eccentrically situated nuclei with a mild degree of nuclear polymorphism. Immunohistochemical staining revealed that the tumor cells were negative for CD3, CD20, and lambda; however, they were positive for CD79a and kappa. The patient subsequently underwent radiotherapy and has been asymptomatic for nine years.