A Case of Schwannoma Arising in the Masseter Muscle

Abstract

Schwannoma is a benign tumor originating from Schwann cells, occurring rarely in the masseter muscle. In this report, we describe a case of schwannoma in the masseter muscle. A 35-year-old man was referred to our hospital because of swelling of the left cheek. A painless elastic hard mass was palpable in the left cheek. No abnormalities were found in the skin, oral mucosa, or cervical lymph nodes. MRI T2-weighted images showed a high signal area with 43×37mm internal nonuniformity and clear boundaries. Although malignant atypical cells were not detected by fine-needle aspiration and incisional biopsy, no definitive diagnosis was obtained. The lesion was diagnosed as a benign tumor of the masseter muscle and resection was performed under general anesthesia. It was located in the masseter muscle without any adhesion to surrounding tissues. No nerves were continuous with the tumor. The tumor was 45×40×30mm in size and was covered with a capsule. Histopathological diagnosis was schwannoma. After the operation, left facial nerve palsy was recognized, but it was completely cured 3 months after the operation. In addition, neither masseter atrophy nor masticatory function was observed. Two years have passed since the operation without recurrence of the tumor.