Intra-thyroid thyroglossal duct cyst: a case report and review of the literature.

Thyroglossal duct cyst (TGDC) is the most common congenital anomaly of thyroid gland. TGDC are ectopic remnants mainly occurring in the midline of the neck, rarely at other sites. Intrathyroidal thyroglossal duct cysts (ITTGDC) are extremely rare and may be confused with thyroid cancer. We herein described a rare case of ITTGDC with a review of the literature. A 47-year-old woman presented with a painless, mobile midline neck mass of 2 months duration. Clinical and imaging investigations suspected thyroid nodule that was classified EU-TIRADS3 on ultrasound. The cytology from fine needle aspiration was categorized as benign. A lobectomy was performed. The histopathologic examination showed a macrovesicular adenoma. Unexpectedly, a 1.2 cm ductal cystic structure with pseudostratified ciliated columnar epithelium was identified adjacent to the thyroid pseudocapsule. It was diagnosed as ITTDGC. Mild lymphocytic thyroiditis was also present. This case highlights the diagnostic challenge of ITTGDC, particularly given its rarity with only few reports documented in the literature. This report, accompanied by a review of the literature, adds to the limited documentation of ITTGDC and underscores the need for awareness of this rare entity among clinicians and pathologists.