Abstract
Primary synovial sarcoma of the thyroid is an extremely rare condition which has only been reported twice in the literature. We herein report a case of highly aggressive and rapidly lethal primary synovial sarcoma of the thyroid. A 72-year-old woman presented with extensive local invasion, rapid progression, and early distant metastasis secondary to primary thyroid synovial sarcoma. The tumor exhibited an atypical histologic and immunohistochemical staining pattern. Detection of SYT/SSX fusion transcript confirmed the diagnosis of synovial sarcoma. Due to the aggressive nature of primary synovial sarcoma of the thyroid gland, early diagnosis and comprehensive treatment including wide resection and postoperative chemoradiation is required.