Cyst characteristics of the four echinococcal species

Species	Larval form in humans	Cyst components	Cyst growth
E. granulosus	Cystic, unilocular, expansile	Metacestode has an internal germinative layer (endocyst) surrounded by a parasite-derived acellular laminated layer (exocyst), which in turn is surrounded by a host-derived adventitial layer (pericyst).	Cells bud internally within the cystic cavity, then vacuolate and become "brood" capsules. Protoscolices develop within the brood capsules.
E. multilocularis	Multilocular, infiltrative	Very thin laminated layer only and no pericyst, which enables tissue invasion.	Germinative layer of the metacestode proliferates within cyst and exogenously to infiltrate host tissue. Cells from the germinative layer can detach and metastasize to other organs.
E. vogeli and E. oligarthrus	Polycystic, expansile	Large cysts with multiple vesicles are separated by septa lined by germinative epithelium. Externally, the cyst is surrounded by fibrous tissue.	Brood capsules bud internally from the germinative epithelium. An expansile and infiltrative polycystic metacestode mass develops.

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