Papillary Thyroid Carcinoma Arising in a Thyroglossal Duct Cyst: Radiologic and Pathologic Correlation in a Young Adult.

Thyroglossal duct cysts are the most common congenital cervical anomalies, arising from incomplete involution of the thyroglossal duct during embryologic thyroid descent. Although typically benign, malignant transformation occurs in approximately 1% of cases, most commonly papillary thyroid carcinoma. We report a case of a 27-year-old female presenting with a progressively enlarging midline neck lump. Ultrasound demonstrated a complex cystic lesion superior to the thyroid gland. Contrast-enhanced computed tomography revealed a cystic structure containing a peripherally hyperattenuating, centrally hypoattenuating nodular component with associated punctate calcifications. Ultrasound-guided biopsy confirmed papillary thyroid carcinoma. The patient then underwent total thyroidectomy, with pathology demonstrating a 1.5 cm papillary thyroid carcinoma arising within a thyroglossal duct cyst, without nodal metastases but with positive margins. Histopathology revealed characteristic papillary architecture with fibrovascular cores lined by atypical epithelial cells. Postoperatively, the patient received radioactive iodine (I-131) ablation therapy and remains disease-free at one-year follow-up. This case highlights the importance of recognizing atypical imaging features within thyroglossal duct cysts, which should prompt further evaluation. Accurate diagnosis relies on the correlation of imaging and histopathologic findings. Early detection and appropriate management are essential, as papillary thyroid carcinoma arising in thyroglossal duct cysts carries an excellent prognosis.