Synchronous oral squamous cell carcinoma and extramedullary plasmacytoma of the tonsil.

Extramedullary plasmacytoma (EP) is characterized by a neoplastic proliferation of plasma cells in a soft tissue site and arises particularly in the head and neck region. We report here an unusual case of maxillary sinus EP coexisting with oral squamous cell carcinoma (SCC) in a patient without any identified environmental risk or predisposing factors. The maxillary sinus mass proved to be radioresistant, with distant metastasis of EP in the tonsil and thoracic skin. The patient subsequently received chemotherapy and showed no evidence of recurrence at 6 months' follow-up. To the best of our knowledge, this is the first case reported demonstrating synchronous occurrence of oral SCC and EP arising in oral cavity.