Echinococcal cyst

Topic Completed: 1 July 2014

Minor changes: 8 October 2021

Copyright: 2002-2019,, Inc.

PubMed Search: Echinococcal cyst breast

Jaya Ruth Asirvatham, M.B.B.S.
Julie M. Jorns, M.D.
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Cite this page: Asirvatham JR, Jorns JM. Echinococcal cyst. website. Accessed October 25th, 2021.
Definition / general
  • See also discussion in liver - nontumor chapter
  • Due to infestation by larval form of Echinococcus granulosus
  • Rare but consider in differential diagnosis of a breast mass in endemic regions
  • Also called hydatid cyst
  • Occurs worldwide, especially in sheep rearing communities
  • Women in the age group of 30 - 50 years are affected
  • Definitive host: dog
  • Intermediate host: sheep
  • Consumption of soil, water or food contaminated by fecal matter of an infected dog leads to infestation by larval form of Echinococcus granulosus
Diagrams / tables

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Life cycle

Clinical features
  • Slow growing lesion, may mimic fibroadenoma, phylloides or rarely intracystic carcinoma
  • May become infected and be indistinguishable radiologically from an abscess
  • Requires a high index of suspicion
  • Peripheral eosinophilia, positive echinococcal antigen immunofluorescence or hemagglutination tests and a history of exposure in an endemic area are clues to the diagnosis
  • Serum Echinococcus hemagglutination test
  • ELISA for echinococcal IgE
Radiology description
  • On mammography, lesions may be well circumscribed, oval or spherical densities, with smooth lobulated margins
  • Peripheral calcification may be present
  • On ultrasound, several classic signs have been described such as double wall sign (cyst wall seen as 2 echogenic layers), snowstorm sign (due to movement of scolices within the cyst), waterlily sign (floating membranes due to detached endocyst / daughter cyst), scroll sign (due to folding of the detached endocyst, J Clin Ultrasound 2014;42:502) (Singapore Med J 2010;51:e72, see figures 1 & 2)
Prognostic factors
  • Excision is curative
  • Reported recurrence rate is 7 - 14%
  • Spillage of protoscolices during surgery may lead to implantation
  • Serological titers may fall slowly postoperatively and a positive titer may not imply recurrence although rising titers are suggestive of recurrence
Case reports
  • Surgical, albendazole may be given to reduce size pre-operatively
Gross images

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Excised hydatid cysts

Multiple cysts and daughter cysts

Echinococcus cyst in the liver

Microscopic (histologic) description
  • The cyst comprises 3 layers: outermost pericyst is fibrous, middle ectocyst layer is laminated, hyaline and acellular and the inner endocyst is the germinative layer which consists of daughter cysts and brood capsules with scolices
  • There may be granulomatous palisading reaction and pseudocyst formation as seen in cutaneous lesions
Microscopic (histologic) images

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Liver: daughter cysts with germinal layer


Laminated cyst wall


Adrenal gland

Echinococcus egg in feces

In sheep

Cytology description
  • Aspiration may yield clear fluid with particulate material which may contain scolices with hooklets (PAS and acid fast positive) and bits of the laminated membrane
Cytology images

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Scolices and hooks

Differential diagnosis
  • Granuloma annulare: if palisading granulomatous inflammation predominates
  • Pseudocyst / fibrous capsule: due to previous procedure, trauma or foreign body; no trilaminar cyst wall or PAS positive material
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