A case of schwannoma arising in the masseter muscle

Abstract

Schwannoma is a benign tumor developing from the Schwann’s sheath of peripheral nerves, constituted of Schwann cells and collagen fibrous matrix. The frequency of occurrence in the oral region is high in the tongue, while rare in the masseter muscle. Here, we report a case of schwannoma in the left masseter muscle. The patient was a 64-year-old man with indolent swelling of the left cheek, measuring 50×45 mm. Magnetic resonance imaging showed a 44 mm tumor with a clear margin. T1-weighted imaging showed a homogeneous signal similar to muscle, while T2-weighted imaging showed an internal non-homogeneous, low signal at the center. The tumor was removed from outside the mouth under general anesthesia. Motor nerve paralysis of the lower lip appeared after surgery but disappeared in two months. The tumor was covered with a capsule, and there was no adhesion with the surrounding tissue. Neural tissue was not found near the tumor. The histopathological diagnosis was schwannoma. Recurrence has not been observed in the 5 years and 11 months after surgery.