PSAT252 Primary Papillary Thyroid Carcinoma Arising from a Thyroglossal Duct Cyst

BACKGROUND: Thyroglossal duct cysts (TGDC) are remnants of the thyroglossal duct tract that do not atrophy and disappear, instead undergoing cystic expansion and often presenting as a midline neck mass. Rarely, carcinomas of the thyroglossal duct cyst occur, either arising as a primary carcinoma or as a cystic metastasis from a primary thyroid cancer; the former are particularly rare. These thyroglossal duct cyst carcinomas most commonly present in the adult population. CASE REPORT: We present the case of a 32-year-old female without any significant past medical history who presented with a non-tender midline neck mass identified as a thyroglossal duct cyst and completely excised; pathology results were positive for a primary papillary thyroid carcinoma with a tumor measuring 1.3 cm in diameter within the TGDC. Thyroid Ultrasound also showed the presence of two nodules measuring 1.4 cm on the right and 1.2 cm on the left, respectively, with fine needle aspiration (FNA) of both the nodules confirming papillary thyroid carcinoma as well. Lymph node FNA was negative for metastatic carcinoma. The patient underwent a thyroidectomy which definitively confirmed both a classic papillary carcinoma as well as an encapsulated, non-invasive follicular variant. In keeping with the original finding of the patient having a primary thyroglossal duct cyst carcinoma, samples from the thyroidectomy had negative tumor margins, and were also negative for any angioinvasion, lymphatic invasion, or extrathyroidal extension. CONCLUSION: While thyroglossal duct cysts are the most common type of congenital neck cyst, primary carcinomas arising from thyroglossal duct cysts are rare. Masses that occur anywhere along the thyroglossal duct tract should be investigated for malignancy, with additional investigation of the thyroid gland for either a primary or secondary thyroid cancer. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.