Echinococcal cyst (hydatid cyst)

The larval form of Echinococcus granulosus, a dog tapeworm, causes infections in many organs, mainly the liver. Imaging studies reveal a solitary cyst, often with a fluid level. An outer, acellular, laminated membrane lines the cyst. The internal, germinal layer gives rise to daughter cysts, each of which containing scolices with numerous hooklets. Scolices may be lost in longstanding cysts with degeneration.

Cytologic diagnostic features

• Fragments of the laminated membrane
• Scolices
• Hooklets

Anaphylactic shock has been reported as an occasional complication of the aspiration of an echinococcal cyst.