BACKGROUND: Thyroglossal duct cyst is a common congenital anomaly of the thyroid gland, usually found centrally. The presence of malignancy occurring in a thyroglossal duct cyst is a rare condition, accounting only for 1% of all cases of thyroglossal duct cyst. This report is of a rare case of papillary carcinoma arising in a thyroglossal duct cyst and includes a review of the literature.

CASE REPORT: A 27-year-old female patient was referred to our department with a painless cystic mass in the neck. After initial physical examination and endocrinology investigations, a fine needle aspiration (FNA) of the cyst was performed. Cytology showed a papillary neoplasm. The patient underwent total thyroidectomy and surgical excision of the thyroglossal duct cyst (the Sistrunk’s procedure). Histopathology of the surgical excision specimen showed a thyroglossal duct cyst with a maximum diameter of 7.5 cm containing a primary invasive papillary carcinoma, measuring 1.5 cm in diameter that infiltrated into the cyst wall. The remaining thyroid gland was normal.

CONCLUSIONS: Thyroglossal duct carcinoma, most commonly papillary carcinoma, is a rare condition that should be considered in patients presenting with cystic midline neck masses. Surgery and complete excision is the main treatment and the optimal patient management includes multidisciplinary consultation in order to improve survival. The diagnosis of malignancy is made postoperatively, as in the present case.

Keywords: Carcinoma, Papillary, Thyroglossal Cyst, Thyroidectomy