A case of solitary fibrous tumor in the floor of mouth

Solitary fibrous tumor (SFT) is a spindle cell tumor of mesenchymal origin.According to the WHO classification of soft tissue tumors, it is classified as a benign malignant intermediate fibrous/myofibrous tumor.However, beginning with a report of SFT outside the pleura in 1991, cases of occurrence in various organs have since been reported.Approximately 5% of cases occur in the head and neck region, and occurrence in the oral cavity is rare.Herein we report a case of SFT in the floor of the mouth.A 69-year-old man presented with the chief complaint of a painless tumor in the floor of mouth.MRI showed a 9 mm nodule in the floor of mouth, and a solid tumor was suspected.Complete resection was performed based on a clinical diagnosis of benign tumor in the right floor of mouth.Histopathological examination revealed a haphazard arrangement of spindleshaped cells and a vascular cavity in a mitotic state.Immunostaining showed positive for CD34 and STAT6, leading to a definitive diagnosis of SFT.One year and eight months have passed since the surgery, and no local recurrence or metastasis has been observed, however long-term follow-up is required.