Papillary Carcinoma Arising in a Thyroglossal Duct Cyst in an Adult: A Rare Case Report and Review of Management

Background: Thyroglossal duct cysts (TGDCs) are the most common congenital midline neck masses. Malignant transformation within a TGDC is rare, occurring in approximately 1% of cases, with papillary carcinoma being the most common histologic subtype. Because TGDCs generally present as benign lesions, carcinoma is often diagnosed incidentally after surgical excision, creating both diagnostic and therapeutic challenges.
Case Presentation: We report the case of a 33-year-old woman with no significant medical history who presented with a slowly enlarging, painless midline neck mass over six months. Physical examination revealed a mobile, non-tender infrahyoid mass that moved with tongue protrusion, without skin involvement or cervical lymphadenopathy. Imaging demonstrated a complex cystic lesion with internal calcifications suggestive of a thyroglossal duct cyst. The patient underwent a Sistrunk procedure. Histopathology revealed a 1.5 cm papillary carcinoma confined to the cyst wall, with clear surgical margins and no evidence of thyroid involvement. No additional surgery was performed. The postoperative course was uneventful, and follow-up showed no recurrence.
Conclusion: Papillary carcinoma arising in a TGDC is rare and difficult to diagnose preoperatively. In carefully selected low-risk patients, the Sistrunk procedure alone may be sufficient. Long-term follow-up is essential to ensure favorable outcomes.