Papillary carcinoma of thyroid in a thyroglossal cyst.

Thyroglossal duct cyst (TDC) is the most common congenital anomaly of the thyroid gland and the most common congenital cervical abnormality in childhood. Carcinoma arising from a TDC is rare, which composes only 1% of TDC cases. Here, we are reporting a case of 50-year-old male with a swelling in the upper left neck region which was progressively increasing in size over 5 years.