(14.03) Primary Papillary Thyroid Carcinoma in a Thyroglossal Duct Cyst

Friday, May 10, 2024

2:25 PM – 2:40 PM CDT

Location: ePoster Showcase, Empire Ballroom Foyer, Level 2

Submitter(s)

Hawra Kamal, MD

fellow
Wayne state university
DEARBORN, Michigan, United States

Introduction : The management of p</span>apillary thyroid cancer arising within a thyroglossal duct cyst (TGDC) can be challenging. This case explores the diagnostic challenges and management of this unusual occurrence.  

Case(s) Description : A 24-year-old female presented with a left-sided neck mass which she noted during a photoshoot. She had no compressive symptoms or symptoms of hypo-hyperthyroidism. Thyroid function tests were normal, and thyroid autoantibodies were negative. A neck ultrasound revealed a large complex cystic mass in the left submandibular gland region.  Follow-up CT neck was concerning for a malignant neoplasm with a possibility of hyoid bone involvement. Fine-needle aspiration was consistent with cyst content but negative for malignancy. A Sistrunk procedure was performed. Histopathology revealed a TGDC containing a primary papillary carcinoma focally eroding bone. Preoperative neck imaging also showed bilateral morphologically normal lymph nodes. The cytology on the right node was benign but the left was indeterminate. She underwent a total thyroidectomy. The final pathology of the thyroid parenchyma was benign. Thyroxine withdrawal I 131 scan revealed tracer uptake in the left thyroid bed but no distant uptake. Post-ablation thyroglobulin was 3 ng/ml, with negative antithyroglobulin antibodies. She received remnant ablation with 30 mCi of I-131. The post-therapy scan was similar to pretherapy.   She has been maintained on levothyroxine with a TSH goal of < 2.5.

Discussion :

The majority of TGDCs are noted in children and adolescents. A third of the cases are seen in adults older than 20 years. Primary carcinoma in the thyroglossal duct remnant is a rare entity and is often diagnosed postoperatively. Therefore, no standard management guidelines are available. Management beyond the Sistrunk procedure has been a topic of debate. The questions without consensus are 1. Need for thyroidectomy in the absence of thyroid nodules. 2. Extent of thyroid surgery. 3. Postoperative radioactive iodine therapy. However, the consensus among most authors is that when there is evidence of cervical metastasis, a regional neck dissection should be carried out. For patients with a TGDC containing only a microscopic focus of thyroid carcinoma that hasn't invaded the cyst wall or demonstrated clinical signs of metastatic spread, limited surgical intervention as a Sistrunk procedure is considered appropriate. Available evidence points to higher age and aggressive histopathology to be associated with worse outcomes. Therefore, total thyroidectomy should be advised in these cases. The use of radio-iodine ablation and TSH suppression treatment can be tailored based on individual risks. Our patient underwent a total thyroidectomy. Considering the presence of hyoid bone involvement, she underwent postoperative remnant ablation for greater ease of follow-up.