Humeral hydatid cyst mimicking a malignant bone tumor

Hydatidosis is a parasitic disease caused by Echinococcus granulosus or, less commonly, Echinococcus multilocularis. The disease occurs mainly in Mediterranean countries, and is considered endemic to that region. The liver and lungs are the organs most often affected; hydatid disease of the humerus is extremely rare. Osseous hydatid disease should be included in the differential diagnosis for cystic masses in any anatomic location, and should be carefully considered if the patient resides in a region where the disease is endemic. This case report describes a pathologically proven hydatid cyst of the humerus that mimicked a malignant bone tumor on plain films. The X-ray, ultrasonographic, and magnetic resonance imaging findings are presented.