An Incidental Primary Papillary Carcinoma Arising in a Thyroglossal Duct Cyst: Report of a Rare Finding.

The thyroglossal duct cysts (TGDCs) are the most common congenital anomaly of the thyroid, usually manifested as painless midline neck mass. Malignancy is very rare and is reported in around 1% of cases as an incidental finding after histopathological evaluation of resected cyst. Papillary carcinoma is the most common carcinoma reported in TGDC. Here, we report a case of 17-year-old-female, who presented with a gradually increasing midline neck mass which moves with swallowing. On imaging a diagnosis of infected TGDC was made. The Sistrunk operation was done and a diagnosis of primary papillary carcinoma arising in a TGDC was rendered histopathologically. The contemporary appearance of papillary carcinoma thyroid was reported in about 20% cases of TGDC carcinoma, thus it is essential to differentiate primary papillary carcinoma arising in a TGDC from those of metastatic papillary carcinoma thyroid by strict diagnostic criteria.