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Echinococcal cyst of lung

Reviewer: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 11 June 2012, last major update September 2011
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Clinical features

● Also called hydatid cyst
● Humans become infected by eating food contaminated with tapeworm eggs, becoming intermediate hosts
● Eggs from dog tapeworm Echinococcus granulosus or E. multilocularis where foxes are the most common definitive hosts; other species rarely cause hydatid diseae in humans
● For E. granulosus, sheep are most important intermediate hosts; for E. multilocularis, rodents are most important intermediate hosts
E. granulosus is more common in humans and is most common cestode infection of the lung
● Eggs hatch in duodenum and spread to liver, lung, bone or elsewhere
E. granulosus cysts are most common in liver, 5-15% occur in lung; pulmonary disease is often secondary to hepatic disease (World J Surg 2001;25:46)
● Larvae lodge in capillaries and incite a mononuclear and eosinophilic inflammatory cell response
● Many larvae die, some encyst
● Pulmonary cysts may be asymptomatic or cause respiratory compromise by compressing airways or lung parenchyma; rarely complicated by Aspergilloma (Br J Radiol 2008;81:e279)
● Cyst rupture may cause fatal anaphylactic shock or pneumonia with consequent development of numerous new cysts throughout lung

Case reports

● 52 year old woman with solid nodule resembling malignancy (Cytojournal 2012;9:13)

Clinical images

Cysts in operative field

Micro description

● Cysts gradually enlarge and years later may be several centimeters in diameter
● Cyst is bilayered and surrounded by fibroblasts, mononuclear cells, eosinophils, multinucleated giant cells
● Daughter cysts usually develop in large mother cyst
● Daughter cysts develop as projections from a germinative layer and form brood capsules
● Degenerating scolices of developing worms produce sediment, so-called “hydatid sand”

Micro images

Contributed by Dr. Hanni Gulwani, New Delhi (India)

Cytology images

2 cm lung nodule

BAL fluid - scolices

End of Lung-nontumor > Infections > Echinococcal cyst of lung

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