Abstract
The primary occurrence of synovial sarcoma (SS) in the thyroid is quite rare. As other SS arise from the head and neck structure, it tends to present poor biological behaviors and is generally treated as a high-grade sarcoma. The present study reports the case of a 31-year-old male who presented a neck mass, involving the thyroid, as shown by ultrasonography. The tumor was resected by total thyroidectomy and diagnosed as SS by histopathology. However, the initial surgery was considered as incomplete (R2) and no adjuvant protocol was followed. At the follow-up, neck recurrences within local lymph nodes were found repeatedly. The tumor grade increased for the metastatic lesions, indicating poorer differentiations with repeated relapses. The accurate evaluations of the primary tumor facilitated it to tailor the initial treatments, otherwise, the prognosis may be deteriorated by inappropriate management.