Malignant Granular Cell Tumor in the Gluteal Region with Unusual Pathologic Features

Malignant granular cell tumors (MGCTs) are very rare soft tissue sarcomas. Definite criteria for pathologic diagnosis and the optimal treatment strategy have not been fully established. Here, we describe a 76-year-old woman with a huge MGCT in the right gluteal region, who developed a local recurrence and died from that tumor 14 months after undergoing an operation for the primary tumor. Although microscopic examination revealed that round and granular tumor cells staining for S-100 protein were dominant, components of the spindle cell sarcoma reacting with alpha smooth muscle actin were partially observed. MGCT is believed to originate from Schwann cells; however, pathologic findings in our case showed both Schwannian and non-Schwannian features. This is the first report on MGCT with these 2 features appearing simultaneously.