Echinococcal cysts may rarely occur in unusual locations. Recognition prior to removal of a cyst is important since incomplete removal can result in anaphylaxis, seeding of new cysts and recurrence.
Unusual sites for an echinococcal cyst include:
(1) subcutaneous tissue, mimicking an epidermoid cyst
(2) skeletal muscle
(3) parotid gland
(4) pancreas
(5) adrenal gland
(6) gallbladder
(7) heart
(8) seminal vesicle
(9) thyroid gland
(10) bone
(11) breast
The parasite may reach the site either by direct inoculation (dog bite, etc) or "metastatic dissemination" from a tiny rupture of an existing cyst.
When to suspect:
(1) history of residing or visiting a country endemic for echinococcosis
(2) past history of echinococcosis
(3) eosinophilia in the peripheral blood (but present in less than 50% of patients)
(4) history of allergic reaction following manipulation of the cyst
If an echinococcal cyst is suspected then it is important to decide if it can be resected intact or not. If it cannot be resected intact then chemotherapy may be given.
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