Background
Branchial cleft cysts are congenital epithelial cysts that arise on the lateral part of the neck from a failure of obliteration of the second branchial cleft in embryonic development. [1]
Phylogenetically, the branchial apparatus is related to gill slits. In fish and amphibians, these structures are responsible for the development of the gills—hence the term branchial (from Greek branchia ["gills"]).
Surgical excision is definitive treatment for branchial cleft cysts. Antibiotics are required to treat any related infections or abscesses. Patients should be reassured that branchial cleft cysts are benign.
Pathophysiology
At the fourth week of embryonic life, the development of four branchial (or pharyngeal) clefts results in five ridges known as the branchial (or pharyngeal) arches, which contribute to the formation of various structures of the head, the neck, and the thorax. The second arch grows caudally and, ultimately, covers the third and fourth arches. The buried clefts become ectoderm-lined cavities, which normally involute around week 7 of development. If a portion of a cleft fails to involute completely, the entrapped remnant forms an epithelium-lined cyst with or without a sinus tract to the overlying skin. [1]
These lesions may be clinically divided into four main types (first, second, third, and fourth branchial cleft cysts) according to their location and the arch involved in their pathogenesis. The majority of branchial cleft cysts arise from the second branchial cleft. [1]
Although most of these cysts are benign, rare cases of malignant transformation have been reported. [2]
Etiology
The branchial cleft cyst is a congenital lesion formed by incomplete involution of branchial cleft structures during embryonic development.
Epidemiology
The exact incidence of branchial cleft cysts in the US population is unknown. In the pediatric population, branchial cleft cysts are the second most common congenital cause of a neck mass. [1] An estimated 2-3% of cases are bilateral. A tendency exists for cases to cluster in families.
Although branchial cleft cysts are congenital in nature, they may not present clinically until later in life, usually by early adulthood. No sexual predilection is recognized for branchial cleft cysts, nor has any racial predilection been reported.
Prognosis
Many branchial cleft cysts are asymptomatic. They may become tender, enlarged, or inflamed, or they may develop abscesses, especially during periods of upper respiratory tract infection, as a consequence of the lymphoid tissue located beneath the epithelium. Spontaneous rupture of an abscessed branchial cleft cyst may result in a purulent draining sinus to the skin or the pharynx.
Depending on the size and the anatomic extension of the mass, local symptoms, such as dysphagia, dysphonia, dyspnea, and stridor, may occur.
After surgical excision of branchial cleft cysts, the recurrence rate has typically been low, at an estimated 3%, unless surgical treatment has previously been performed or recurrent infection has developed, in which case rates as high as 20% have been reported.
In a study using data from the American College of Surgeons (ACS) National Surgical Quality Improvement Program adult (NSQIP) and pediatric (NSQIP-P) databases, Moroco et al assessed outcomes of surgical excision of branchial cleft cysts in children (n = 1775) and adults (n = 677). [3] The postoperative complication rate was low in both groups: 3.9% in children and less than 1% in adults. In adults, smoking status had a significant effect on the complication rate. The readmission rate was also low in both groups: 1.1% in children and 1.2% in adults.
In another study that used NSQIP-P data, Raghavan et al reported a postoperative complication rate of 3% in pediatric patients who underwent excision of a branchial cleft cyst. [4]
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First branchial cleft cyst, type II. Contrast-enhanced axial computed tomography scan at the level of the hyoid bone reveals an ill-defined, nonenhancing, water attenuation mass (m) posterior to the right submandibular gland (g).
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Second branchial cleft cyst. Contrast-enhanced axial computed tomography scan at the level of the hyoid bone reveals a large, well-defined, nonenhancing, water attenuation mass (m) on the anterior border of the left sternocleidomastoid muscle(s).
