SUN-618 An Unusual Case of Papillary Thyroid Cancer within a Thyroglossal Duct Cyst

Background: During gestation, the thyroid gland arises from endodermal tissues, and starts at the foramen cecum, then descends into the neck through the thyroglossal duct, and disappears at 8-10 weeks of gestation. Thyroglossal duct cysts arise from incomplete obliteration of the thyroglossal duct, and may contain thyroid tissue. Although the incidence of thyroid cancer has been rising, it is still relatively uncommon compared to other cancers, with papillary thyroid carcinoma being the most common type. However, in rare cases, thyroid carcinoma can occur within the thyroglossal duct cyst. We present a rare case of a young female with papillary thyroid carcinoma within a thyroglossal duct cyst. Case Presentation: A 28-year old female noticed an enlarging midline neck mass over the course of 5 years. She was initially evaluated by otolaryngology. CT neck revealed a heterogeneous large midline neck mass, measuring 5.7 x 3.6 x 4.99cm, which was separate from the thyroid gland. Submandibular lymph nodes were also enlarged. Pathology of core tissue biopsy of the mass demonstrated papillary thyroid carcinoma. She underwent thyroglossal duct cyst resection and total thyroidectomy with neck dissection. Pathology report was positive for papillary thyroid carcinoma, arising from thyroglossal duct cyst measuring 4.2cm. Three out of 16 lymph nodes were positive for papillary thyroid carcinoma. Thyroid gland had no evidence of malignancy. Postoperatively, thyroid hormone suppression therapy was started and she was treated with radioactive iodine ablation. Discussion: Thyroglossal duct cysts are the most common abnormalities in thyroid gland development. They are usually managed with excision, specifically the Sistrunk procedure, where the cyst, along with the entire tract and part of the hyoid bone is excised. In rare cases, thyroid cancer can arise within the thyroglossal duct cyst. When this occurs, management can sometimes be controversial, as there are no specific guidelines, and severity of disease varies. It is important to recognize that evaluation of these type of patients should include the thyroid and regional lymph nodes, in order to ensure that the thyroglossal duct cyst carcinoma is primary, and not a metastasis from a primary thyroid carcinoma. In cases where the malignancy is confined to the cyst, the Sistrunk procedure alone can be done. If malignancy is found in the thyroid and regional lymph nodes, the Sistrunk procedure in addition to total thyroidectomy is completed, and then post-operative management is the same as for differentiated thyroid cancer including radioactive iodine ablation. References Pellegriti G, Lumera G, Malandrino P, et al., Thyroid Cancer in Thyroglossal Duct Cysts Requires a Specific Approach due to Its Unpredictable Extension, JCEM, Volume 98, Issue 2, 1 February 2013, Pages 458-465.