Thyroglossal duct cyst is common midline mass, which is related to hyoid bone and may show signs of inflammation. Carcinoma arising in the thyroglossal duct cyst is rare, occuring in less than 1% of thyroglossal duct cyst. Papillary adenocarcinoma is the most common histologic type(75-85%). The initial treatement of choice is wide excision of the tumor bearing tissue(Sistrunk procedure), resection of associated lymph node alone is enough when they are small and isolated, but a modified neck dissection must be done if regional involvement is more extensive. Its prognosis is excellent(the incidence of regional lymph node metastasis is 7% compare to 89% for papillary cancer of thyroid gland proper).