General Information
Echinococcus granulosus is a species of tapeworm found in the intestines of dogs and related carnivores whose larval forms produce different types of hydatid disease. Human infection is usually acquired accidentally from close association with dogs. Organisms are ingested, invade the intestinal wall, enter the circulatory system and are filtered out in various organs. The liver is most commonly infected site. Infections usually lead to the formation of cystic, polycystic or proliferative (alveolar) lesions (hydatid cysts).

Cytology
Long oval structures
May see several heads of parasite
Numerous hooklets and scolices
Detached hooklets seen in refractile structures
Infammatory cells, including eosinophils and/or granulomas, compose the background

Special Note
FNA not preferred method of evaluation due to risk of anaphalactic shock caused by cyst fluid into the surrounding tissue.

For more info go to: Hydatid Cyst