Hydatid Cyst of the Thyroid Gland With Concurrent Hepatic Involvement: A Rare Case Report

Hydatidosis, caused by Echinococcus granulosus, most commonly affects the liver and lungs, while thyroid involvement is exceptionally rare and can mimic other cystic thyroid lesions. We report a 40-year-old woman with no history of animal exposure who presented with anterior neck swelling, odynophagia, and abdominal discomfort. She had a prior history of hepatic hydatid cyst treated in 2018. Thyroid ultrasonography revealed a left subcapsular mass measuring 50 × 38 × 24 mm containing a bilobulated internal cyst (27 × 20 × 10 mm) without significant vascularity. Abdominal imaging demonstrated a large subhepatic multiseptated cyst (115 × 90 × 60 mm) with double-layered septations, suggestive of recurrent hydatidosis. The patient underwent left thyroid lobectomy, and histopathological examination confirmed a hydatid cyst characterized by a laminated membrane and germinal layer, along with surrounding granulation tissue, fibrosis, and multinucleated giant cell reaction in the adjacent thyroid parenchyma. Thyroid hydatid cysts are exceedingly uncommon and may be easily misdiagnosed as other cystic thyroid lesions based on clinical and radiologic findings. Therefore, in endemic regions, hydatid disease should be considered in the differential diagnosis to ensure accurate diagnosis and appropriate management.