A case of solitary fibrous tumor arising from the palatine tonsil.

Solitary fibrous tumor (SFT) is a distinctive, relatively uncommon soft-tissue neoplasm that usually arises from the pleura. It occurs at various sites; head and neck lesions are very rare. While most of these tumors have a benign course, a small number have malignant potential. We describe a rare case of SFT arising from the left palatine tonsil in a 66-year-old Japanese woman. The mass was completely resected. Immunohistochemical studies were strongly positive for CD34 and bcl-2, mildly positive for phosphorylated protein kinase B and phosphorylated extracellular signal-regulated kinase 1/2, and negative for platelet-derived growth factor receptor alpha and p53. These findings suggested that this tumor was benign. The patient showed no evidence of recurrence during 2 years of follow-up. We believe that the candidate prognostic marker should be checked to distinguish malignant from benign SFTs.