We herein report a case of squamous cell carcinoma (SCC) arising in a pectoralis major musculocutaneous (PMMC) flap used for reconstruction after the resection of tongue cancer. A 54-year-old woman underwent resection of tongue SCC, right modified radical neck dissection, and reconstruction with a forearm flap in 2010. Soon after the surgery, another reconstruction was performed with a PMMC flap owing to necrosis of the forearm flap. She was making steady progress, but SCC was found in the center of PMMC flap, and the lesion was resected 5 years after the first surgery. There has been no finding of recurrence for over 1 year. There are some hypotheses on the causes of tumorigenesis in reconstructive flaps, such as chronic stimuli, mucosalization of the skin of the flap, and human papillomavirus (HPV) infection. Our patient showed persistent contact of the flap with the teeth due to immobilization of the flap, and immunohistochemical expression of p16, which is induced by HPV infection in dysplastic epithelium and SCC. Therefore, we considered that multiple factors were involved in the carcinogenesis in the PMMC flap. It is important to remove the stimulus and perform long-term follow up owing to the risk that SCC might develop in the reconstructive flap.
