Epstein-Barr virus-associated smooth muscle tumor of the tonsil.

Smooth muscle tumors of the tonsil are rare. Recently, the occurrence of Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) has been increasingly recognized in immunocompromised patients, mainly post-transplantation and AIDS patients. The clinicopathologic features of EBV-SMT are different from conventional smooth muscle tumors. To the best of our knowledge, EBV-SMT involving the tonsil in an AIDS patient has not been reported. A 27-year-old man presented with a 2.2cm right tonsillar mass six months after AIDS diagnosis. The tumor was composed of a cellular proliferation of oval to spindle-shaped cells with mitotic count up to 10 in 10 high-power fields. The diagnosis of EBV-SMT was confirmed by in situ hybridization for EBV-encoded RNA (EBER) transcripts. Synchronous lesions were also detected in the liver and peritoneum by an abdominal computed tomographic scan. EBV-SMT should be included in the differential diagnoses of a mesenchymal tumor in immunocompromised patients, and in the differential diagnoses of a smooth muscle tumor occurring in uncommon sites including the tonsil.