Although flap reconstruction for soft tissue defects after resection of oral cancers such as tongue cancer contributes to functional recovery, malignant tumors such as squamous cell carcinoma may develop on the flap. A rare case of squamous cell carcinoma on a flap 8 years after reconstruction with a forearm flap following resection of tongue cancer is reported. The patient was a 76-year-old man. After chemotherapy for squamous cell carcinoma of the left tongue, partial tongue resection, left shoulder hyoid muscle upper neck dissection, and forearm flap reconstruction were performed under general anesthesia. Eight years after the operation, an outward-growing mass with induration was found on the reconstructed flap, and squamous cell carcinoma was diagnosed. Partial tongue resection was performed under general anesthesia. The wound was sewn to reduce the volume of the tongue and shape it. A complete denture was prepared 9 months after the operation. Three years have passed since the operation, but no recurrence has been observed, and the patient’s course has been good. There are various possible causes for flap carcinogenesis, but in this case, it was considered that the flap had become cancerous due to chronic irritation by the denture.
