PSAT278 A Curious Case of Thyroglossal Duct Cancer

INTRODUCTION: Thyroglossal duct (TGD) cyst is a common congenital anomaly. Thyroid cancer rarely occurs in TGD cysts, affecting less than 1% of cysts. Here we present a case of TGD cancer presenting as a central neck mass. CASE PRESENTATION: 60 y.o female presented to her primary care physician with a neck mass without any compressive symptoms. She had no history of head/neck radiation exposure and no family history of thyroid cancer. She was noted to have a non-tender central neck mass with palpable cervical lymphadenopathy. Neck ultrasound revealed a 5.7 cm multilobulated cystic and solid mass anterior to the thyroid gland. CT scan of the neck revealed a lobulated mixed solid cystic mass at the level of the thyroid cartilage projecting anteriorly, with an abnormal right submandibular lymph node measuring 2.2×1.0 cm. She was evaluated by ENT and underwent resection of the neck mass and the hyoid bone (Sistrunk's procedure). Level 1b lymph node was also removed. Operative findings were concerning for a malignant process. This was confirmed on pathology with findings of TGD papillary thyroid cancer (PTC) and level 1b lymph node demonstrating metastatic PTC with cystic features. She was then referred to endocrine. Thyroid ultrasound revealed multiple bilateral intermediate suspicion nodules. Left inferior thyroid nodule was noted to have high suspicion sonographic features with abnormal right sided level 2 and 3 lymph nodes. She was referred for total thyroidectomy, pathology revealed multifocal PTC with lymph node involvement with extra nodal extension and metastasis to the left sternohyiod muscle, pT2, pN1b, AJCC stage 2. 6-week post-surgical labs revealed TSH of 1.69 mIU/L (ref range 0.40-4.50), thyroglobulin level of 0.8 ng/ml (ref range athyrotic <0.1), with undetectable thyroglobulin antibodies <1 IU/ml (ref range < or = 1 IU/mL). She underwent RAI with 104.6 mci. I-131 Metastatic survey revealed increased uptake in the thyroid bed, otherwise no increased activity elsewhere. Stimulated TSH and Thyroglobulin levels were done but not collected appropriately and therefore not mentioned here. Repeat labs 12 weeks after RAI revealed a TSH of 2.86 mIU/L, Thyroglobulin level of 0.2 ng/ml, and undetectable Thyroglobulin antibody. CONCLUSION: There are no standardized guidelines for management of TGD cancer given the rarity of this condition. FNAB (Fine need aspiration biopsy) may be associated with high false negatives due to inadequate sampling, given the cystic nature of these lesions. In majority of these cases definitive diagnosis of cancer is made after excision of the TGD cyst. Some experts favor a conservative approach via Sistrunk's procedure and pursuing total thyroidectomy if there is high suspicion of thyroid gland involvement as well. Whereas other authors have suggested a more aggressive approach with total thyroidectomy even without evidence of concomitant involvement of the thyroid gland. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.