Concurrent Papillary Thyroid Carcinoma and Synovial Carcinoma of the Neck in an Adult Male

Introduction: Synovial sarcoma makes up 8–10% of all soft tissue sarcomas, and constitutes 3–10% of all sarcomas occurring in the head and neck region. It shows male predominance (3:2), and the mean age of presentation is 30 years.   Case Report: A 51-year-old gentleman presented with right-sided neck swelling which had been progressively increasing in size for the past 2 years. A computed tomography (CT) scan revealed a large heterogeneously enhancing mass on the right side of the neck measuring 7.5 × 6.2 cm. Biopsy of an enlarged node revealed papillary thyroid carcinoma. The patient subsequently underwent total thyroidectomy with right neck dissection. Final histopathology revealed a papillary carcinoma of the thyroid, and the right-sided mass was shown to be monophasic synovial sarcoma.   Conclusion: We present a case of a concurrent pathology of neck papillary thyroid carcinoma with monophasic synovial sarcoma. We experienced difficulty in diagnosis and misdirection due to raised C-reactive protein (CRP) levels, until final histopathology of the neck mass.