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Clinical Problem Solving: Radiology
November 2005

Radiology Quiz Case 3: Diagnosis

Author Affiliations


Arch Otolaryngol Head Neck Surg. 2005;131(11):1029. doi:10.1001/archotol.131.11.1029

Echinococcosis is a parasitic disease that is caused by the cestodes of the genus Echinococcus. Infections due to Echinococcus granulosus, which is the most common species, are still relatively widespread in the Mediterranean countries.1 The infestation occurs either by direct ingestion or indirectly from contaminated water or food. The primary hosts in echinococcal infestations are dogs; the intermediate hosts include sheep, cattle, horses, and, occasionally, humans.1 In man, E granulosus larvae form a primary cyst, which can continue to increase in size to 20 cm in diameter.2 Typically, echinococcosis consists of a single, unilocular cyst; however, 20% to 30% of cases may have several cysts in 1 organ or 1 cyst in multiple organs.3 A hydatid cyst has a trilaminar wall. The outermost layer, which is called an ectocyst, is composed of compressed host tissue. The 2 inner layers are formed by the parasitic origin. The intermediate layer, or the germinal layer, is responsible for the cyst growth; it also gives rise to “hydatid sands,” which are brood capsules for daughter cysts, in which scolices are formed.1 Hydatid cysts develop most frequently in the liver (65%), followed by the lungs (25%) and, rarely, the brain, eyes, heart, bone, or other internal organs.1 Information on the incidence of echinococcal manifestations in the head and neck region is extremely limited, with few case reports in the English-language literature.4-10 The differential diagnosis of a lateral cervical cystic lesion includes branchial cyst, cystic higroma, dermoid cyst, and cystic metastases.