A Case of Papillary Thyroid Carcinoma Located in the Pyramidal Lobe Mimicking Papillary Carcinoma Arising from a Thyroglossal Duct Cyst

Abstract

We report a case of papillary thyroid carcinoma occurred on the caudal side of the hyoid bone. A 49-year-old woman presented with infrahyoid swelling and pain of the anterior neck. Ultrasonography showed a hypoechoic mass located on the caudal side of the hyoid bone and a hypoechoic mass with microcalcification in the left lobe of the thyroid gland. Both masses were diagnosed as papillary carcinoma by fine needle aspiration cytology. The preoperative diagnosis was papillary carcinoma in the left lobe of the thyroid gland, and pre-laryngeal node metastasis. On the other hand, it was also possible that the pre-laryngeal nodule was papillary carcinoma arising from the thyroglossal duct cyst or the pyramidal lobe. And therefore, total thyroidectomy with lymph nodes dissection in the central neck and pre-laryngeal nodule resection were performed. The pre-laryngeal nodule was continuous with the pyramidal lobe. Histopathologically, there were no findings suggestive of the structure of the thyroglossal duct cyst and the final diagnosis was papillary thyroid carcinoma located in the pyramidal lobe. In general, it is difficult to distinguish between thyroglossal duct cyst carcinoma and papillary thyroid carcinoma located in the pyramidal lobe, where an accurate diagnosis based on the adequately examined histopathological findings is required. The case was interesting to have papillary carcinoma in the left lobe of the thyroid as well.