Primary hydatid disease of the soft tissue.

Human hydatid disease is caused by the larval form of the tapeworm genus Echinococcus. The ova hatch in the small intestine, penetrate the intestinal wall, pass through the portal vein into the liver, lungs, and other tissues, and develop into a hydatid cyst. Hydatid disease is endemic in many parts of the world; in the Mediterranean Countries, the Middle and Far East and South America. Soft tissue hydatid disease without the liver and the lung involvement occurs in 2.3% of patients reported from endemic areas. Hydatid disease should be considered in the differential diagnosis of all cystic masses in all anatomic locations especially in endemic areas.