A case of recurrent solitary fibrous tumor of the mouth floor

Solitary fibrous tumors （SFTs） are rare lesions with a predilection for developing in the pleura. Recently, SFTs have been occasionally reported to occur in other regions, including the head and neck. Clinically and histologically, 13 ％ to 37 ％ of pleural SFTs show malignant behavior, but extrapleural SFTs are hardly ever malignant. However, extrapleural SFTs have been reported to recur or to become malignant in the oral cavity. We report on a 38-year-old Japanese woman who presented with a recurrent SFT of the mouth floor, which had been diagnosed as angioleiomyoma and resected 8 years previously. Histological and immunohistochemical re-examination of present and past specimens revealed that this was a case of recurrent SFT. Because recurrent SFT in the oral region has not been reported previously, its clinical behavior is poorly understood. Our case emphasizes that oral SFTs should be followed over the long term because of their intermediate malignant behavior.