Branchial cleft cyst
|Branchial arch fistula|
Fistulography of a right branchial cleft sinus.
|Classification and external resources|
|ICD-10||Q18.0 (ILDS Q18.020)|
A branchial cleft cyst is a congenital epithelial cyst that arises on the lateral part of the neck usually due to failure of obliteration of the second branchial cleft (or failure of fusion of the second and third branchial arches) in embryonic development. Less commonly, the cysts can develop from the first, third, or fourth clefts.
The cyst wall is composed of either squamous or columnar cells with lymphoid infiltrate, often with prominent germinal centers. The cyst may contain granular and keratinaceous cellular debris. Cholesterol crystals may be found in the fluid extracted from a branchial cyst.
Branchial cleft cysts are remnants of embryonic development and result from a failure of obliteration of one of the branchial clefts, which are homologous to the structures in fish that develop into gills.
Four branchial clefts (also called "grooves") form during the development of a human embryo. The first cleft normally develops into the external auditory canal, but the remaining three arches are obliterated and have no persistent structures in normal development. Persistence or abnormal formation of these four clefts can all result in branchial cleft cysts which may or may not drain via sinus tracts.
- First branchial cleft cysts are rare (less than 1%) and typically originate in the angle of the mandible and extend to the external auditory canal. They are often associated with the facial nerve.
- Second branchial cleft cysts account for a majority of branchial cleft cysts and can be found along the anterior border of the Sternocleidomastoid muscle. If sinus tracts are present, they typically drain into the tonsillar fossa, found between the palatoglossal arch and the palatopharyngeal arch.
- Third and fourth branchial cleft cysts are rare. They are located about 2/3 of the way down the SCM anteriorly, usually lower than second branchial cleft cysts. Sinus tracts, if present, ascend along the carotid sheath posteriorly to the internal carotid artery, under the glossopharyngeal nerve, and over the vagus nerve and hypoglossal nerve to open into the piriform sinus or thyrohyoid membrane.
Most branchial cleft fistulae are asymptomatic, but they may become infected. The cyst, however, usually presents as a smooth, slowly enlarging lateral neck mass that may increase in size after an upper respiratory tract infection.
Conservative (i.e. no treatment), or surgical excision. With surgical excision, recurrence is common, usually due to incomplete excision. Often, the tracts of the cyst will pass near important structures, such as the internal jugular vein, carotid artery, or facial nerve, making complete excision impractical.
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