[Primary hydatid cyst of the thyroid, an unusual localisation of hydatidosis]

Echinococcus granulosus, responsible for hydatidosis, most often lodges in the liver and lungs, but is found in other organs of the body in 10% of cases.

A painless, left cervical tumefaction suddenly developed in a 28-year-old Portuguese man. After thyroid lobectomy with isthmusectomy, the pathology findings led to the diagnosis of hydatidosis.

The thyroid is a rare location for a hydatid cyst. Diagnosis can be difficult and fine-needle aspiration cytology is not usually helpful. Treatment requires surgical excision, and administration of benzimidazole derivatives to prevent recurrence.