A cystic lesion adjacent to the cystic duct diagnosed as ectopic thyroid tissue: a laparoscopic case report.

Ectopic thyroid tissue is an uncommon developmental anomaly, and involvement of the hepatobiliary region-particularly near the gallbladder neck or cystic duct-is extremely rare. Such lesions may mimic primary biliary or gallbladder masses, creating diagnostic and therapeutic uncertainty. We report a 50-year-old woman with a 2-year history of intermittent right upper quadrant abdominal pain. Contrast-enhanced CT demonstrated a well-defined hyperdense lesion at the hepatic hilum adjacent to the gallbladder neck, measuring 22 × 14 mm (∼80 HU on non-contrast; 119 HU arterial; 104 HU venous), with indistinct borders from the gallbladder. A biliary or gallbladder-associated tumor could not be excluded, and further evaluation with MRI and PET-CT was recommended. The patient declined additional imaging due to financial constraints and strongly requested operative management. Laparoscopic cholecystectomy with en bloc resection of the hilar lesion was performed. Intraoperative frozen-section analysis and final histopathology revealed benign ectopic thyroid tissue composed of mature, well-differentiated thyroid follicles without atypia. Postoperative thyroid ultrasound showed a normal orthotopic thyroid gland. The patient recovered uneventfully and remained symptom-free at follow-up. Ectopic thyroid tissue adjacent to the gallbladder neck is an exceptionally rare cause of a hilar mass. Surgeons should consider this entity in the differential diagnosis of gallbladder neck or porta hepatis lesions of uncertain origin and rely on histopathology to guide appropriate, conservative management.