Malignant peripheral nerve sheath tumors (MPNSTs) are sarcomas derived from peripheral nerves and have high rates of local recurrence and metastasis. We report a case of an MPNST on the cheek that was discovered following trauma. A 75-year-old man experienced a fall while riding a bicycle and injured his face. The swelling of his left cheek did not improve, and he was referred to our department. No bone fracture was observed on image-based examination, and the patient was followed up. Magnetic

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... esonance imaging one month after the injury revealed a solid lesion 40×35×25mm in size in the left masseter muscle, and biopsy revealed a malignant spindle cell tumor. The tumor was resected under general anesthesia, and the histopathological diagnosis was MPNST. Local recurrence was observed 4 months after the surgery. Therefore, recurrent tumor resection was performed, and the tumor was found to infiltrate the facial nerve. External irradiation of 66Gy was performed postoperatively. Eighteen months after the surgery, no local recurrence or distant metastasis was observed. For MPNSTs, wide excision with a sufficient safety margin is the first choice for treatment, but functional preservation and esthetic considerations are required in the head and neck region.