Yeung Wai Hung, Wong Ka Fai, Leung Siu Kee.
Papillary carcinoma within thyroglossal duct cyst (TGDC) is rare. We present 3 cases of papillary thyroid carcinoma out of 75 cases (4%) of thyroglossal cyst operated in our hospital in last 13 years. All three cases were female. They belonged to age 73, 16 and 30. First case preoperatively found irregular hard mass, heterogeneity with calcification on Ultrasound and solid enhancing component, invading right neck strap muscle and prominent submental lymph nodes on CT scan. Second and third case had no preoperative distinguishing features of malignancy. All were managed with Sistrunk’s operation and total thyroidectomy with or without lymph node dissection. For total thyroidectomy histopathology report, first case showed different tumour morphology likely due to second primaries. Second case showed papillary carcinoma. Third case showed lymphocytic thyroiditis. Cervical lymph node metastasis was noted in pathology report in first and second case. Hypocalcemia was noted in second and third case and manged with calcium supplement. All of them underwent radioactive iodine and subsequently thyroid hormone suppression therapy. They were being followed up for 4 years in first case and 10 years in second and third case at the time of review. There is no recurrence and 5 years survival is 100%. Thyroid carcinoma found in thyroglossal cyst is well documented. This should be discussed with patient in management of thyroglossal cyst. Prognosis is good especially with papillary thyroid carcinoma.