A Case of High-Grade Myofibrosarcoma Originating From Masseter Muscle

Myofibrosarcoma is a rare malignant tumor originating from myofibroblasts. It is classified into low-grade, intermediate-grade, and high-grade according to the histological characteristics. High-grade myofibrosarcoma is reported very rarely worldwide, and its recurrence and metastasis are known to be more common. Myofibrosarcoma is diagnosed by histopathologic examination, and its treatment is complete surgical excision. With a review of literature, we report a case of myofibrosarcoma originating from the right masseter muscle in a 73-year-old male patient who complained of a right chin mass for 4 months. The MRI findings revealed a 4.8 cm-sized heterogeneous contrast-enhancing mass in the right masseter muscle with direct invasion into the ipsilateral medial pterygoid muscle and the mandible body. The patient was treated with margin-free surgical excision, including marginal mandibulectomy, and a highgrade myofibrosarcoma was finally diagnosed as the pathologic finding. Adjuvant radiation therapy was performed as a subsequent treatment, and no recurrence has been observed during follow-up for 1 year.