The branchial cleft cyst, or cervical lymphoepithelial cyst, is a unilateral, soft-tissue swelling that typically appears in the lateral aspect of the neck, anterior to the sternocleidomastoid muscle. It is clinically apparent in late childhood or early adulthood. The cysts, by definition, do not physically connect with the skin or aerodigestive tract.
At least four theories have been proposed regarding the origin of the branchial cleft cyst. These include incomplete obliteration of branchial mucosa, persistence of vestiges of the precervical sinus, thymopharyngeal ductal origin and cystic lymph node origin.1–3
Surgical excision of the branchial cleft cyst is considered curative, with recurrence unlikely if all remnants are removed.
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SOURCE OF BRANCHIAL CYSTS
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The branchial apparatus that begins to form in the second week of fetal life and is completed by the sixth or seventh week4 is probably the structure most widely believed to be the source of branchial cysts; however, definitive data remain elusive.3 Proponents of this theory point to incomplete closure or incomplete obliteration of the fetal branchial arches, pouches or both as the source of the anomaly.5 Specifically, the lack of degeneration of the cervical sinus created by the growth of the second arch over the third and fourth arches is the proposed cause.6 The third and fourth arches thus overlaid by the second arch persist as small pockets with their ectodermal epithelium. These pockets usually fill in during fetal development; however, when they do not, cysts, sinuses and fistulas may arise later.7 These anomalies represent fusional lesions.8
In normal human development, the branchial arches rise with cranial nerves V, VII, IX, X and XI. The branchiomeric muscles include muscles of mastication; anterior belly of the digastric muscle; mylohyoid, tensor tympani and tensor palatine muscles; muscles of facial expression; as well as muscles involved with the hyoid bone and pharynx. Skeletal derivatives from the branchial apparatus include the ossicles, sphenomandibular ligament, styloid process, hyoid bone and laryngeal cartilages. The middle ear and eustachian tubes, the palatine tonsil, thymus and parathyroid glands are derived from the pouches.9–11 It is of note that even in the presence of a branchial cyst, the above structures usually develop without notable deformity or loss of function.
Several authors have discarded the branchiogenic theory in favor of the cystic cervical lymph node or salivary gland inclusion theory.2,12,13 In 1949, King2 concluded that changes within the cervical lymph nodes caused an inflammatory response leading to a lateral neck swelling, which he termed "lateral lymphoepithelial cyst."
In 1959, Bhaskar and Bernier13 examined 468 specimens submitted as branchial cleft cysts and interpreted 96 percent of them to be cystic changes in regional lymph nodes. The cystic change was caused by epithelial entrapment within the node at the time of development. In addition, these authors noted that the parotid gland develops at the same time as the regional lymph nodes and speculated that this was the origin of the entrapped epithelium. Furthermore, Bhaskar and Bernier13 observed that the size of the lesion often varied with concurrent infections in the patient. In view of their findings, they suggested the term "benign cystic lymph nodes" or "benign lymphoepithelial cysts."
The authors use the term ‘branchial cleft cyst’ to refer to these lesions, which can be considered synonymous with the cervical lymphoepithelial cyst.
The controversy over the etiology of the swellings has given rise to a multitude of terms used (presumably) to describe the same lesion. This makes the study of these lesions more difficult.
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DEFINITIONS
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We use the term "branchial cleft cyst" to refer to these lesions, which can be considered synonymous with the cervical lymphoepithelial cyst. Howie and Proops14 defined the branchial cysts (or lymphoepithelial cysts) as "lesions found behind the angle of the mandible in the anterior triangle of the neck at the junction of the upper third and lower two-thirds of the sternocleidomastoid muscle. The cysts have a lining of stratified squamous epithelium resting on a complete or incomplete band of lymphoid tissue with part of the cyst wall resembling a lymph node."
Several authors of case reports, however, have reported these lesions in other places. Golledge and Ellis3 defined these cysts according to two parameters: position and histology. With regard to position, the lesion must lie outside the midline of the neck or within any position in the lateral aspect of the neck. With regard to histology, the cyst lining is squamous or columnar and is surrounded by lymphoid tissue. The lymphoid tissue generally has a follicular pattern with germinal centers or a diffuse bandlike pattern.12 The lining epithelium has been described as stratified squamous or low columnar, and evidence of keratinization may be seen when stratified squamous epithelium is present. Some authors have noted the presence of hair follicles and sebaceous and sweat glands within the cyst.2
Regardless of etiology, it is essential to understand the differences between a cyst, fistula and sinus. Although this may seem somewhat basic, the literature is replete with erroneous use of these terms.10,11 This is especially troublesome when speaking of branchial cleft cysts because some have suggested that cysts are wholly different from fistulas and sinuses, in regard to their time of development, clinical presentation, histology and familial tendencies.9–11 Some investigators doubt a common etiology between the cysts and sinuses. Many surgeons believe that congenital lateral cervical sinuses and fistulas result from the branchial apparatus; however, it is possible that many mechanisms may lead to branchial anomalies.3,7,11
Regarding age at presentation, Telander and Deane7 found in their survey that sinuses and fistulas typically arise in the first decade of life and to a lesser extent in the second decade, whereas cysts occur in the adolescent and adult. Congenitally presented sinus tracts usually are the result of spontaneous or surgical drainage from a cyst and frequently have a familial incidence.5 Microscopically, cysts are lined by stratified squamous epithelium lying on top of lymphoid tissue, with part of the wall resembling a lymph node.14
In contrast, sinuses and fistulas usually have a persistent opening to the exterior and muscular tubes lined with respiratorylike epithelium.10,11 The pattern of inheritance is consistent with an autosomal gene having incomplete penetrance.15 As suggested by Howie and Proops14 and Chandler and Mitchell,12 tubelike lesions should be called fistulae if they are open on each end, and sinuses if they are open only on one end. The definition of a cyst in this context is a closed pouch without opening to the skin, alimentary canal or pharynx.12,13
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PRESENTATION AND DIAGNOSIS
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The branchial cleft cyst typically is a slow-growing, fluctuant mass that becomes apparent in the second and third decades of life.3,7,16 A close association with the external ear, angle of the mandible and upper lateral aspect of the neck usually is observed, which is consistent with the most commonly accepted etiology (that is, coincident with the fetal location of the branchial apparatus). The swelling typically develops in the junction between the upper one-third and lower two-thirds of the anterior sternocleidomastoid muscle, but it can occur at any level from the hyoid to the suprasternal notch.16 Chandler and Mitchell12 described the location as being between the tragus and clavicle.
The branchial cleft cyst typically is a slow-growing, fluctuant mass that becomes apparent in the second and third decades of life.
The cyst generally is movable in all planes and is motionless during swallowing.16 Twenty to forty percent of patients relate its appearance to a recent upper-respiratory–tract infection, odontogenic infection or even to pregnancy.4,6,16,17 If large enough, the anomalies can cause asymmetry of the neck, as well as dyspnea, dysphagia and dysphonia.4 The swelling usually is unilateral, but cases of bilateral cysts/sinuses have been reported, with an incidence of 2 to 3 percent.15,17 When bilateral cysts/sinuses develop, there seems to be a familial tendency.4,5 Some believe there is an overall familial tendency for the development of unilateral cysts as well, but these authors seem to be in the minority.4
There is no sex predilection according to most observers,16 but some researchers have noted that the cyst appears more commonly in males than in females.7,16 In addition, no right- or left-sided tendency exists. Inflamed cysts may become abscessed, which eventually can lead to rupture. A permanent sinus may form or recurrent cyst formation and infection may occur.12
Differential diagnosis.
The clinical differential diagnosis of these lesions includes tuberculous lymphadenitis, lipoma, cystic hygroma, carotid body tumors, thyroglossal duct cysts, metastatic neoplasms, lymphomas, suppurative lymphadenitis, branchial fistulas/sinus dermoid cysts, neurofibroma, hemangioma, lymphangioma, teratoma, parotid neoplasm, ectopic salivary tissue, laryngocele and plunging ranula.4,5,13 Clinicians must consider malignancies involving the lymph nodes, either primarily or secondarily.5
Diagnosis of branchial cleft cyst.
The diagnosis of branchial cleft cyst is made primarily by medical history, clinical manifestations and exclusion. Preoperative ancillary diagnostic procedures include computed tomography, or CT, sonography and fine-needle aspiration, or FNA. CT may be particularly useful not only to visualize the full extent of the lesion, but also to delineate its association with adjacent structures.
These lesions are deemed amenable to sonography because of their typically superficial nature.18 The sonomorphologic findings typically yield a rounded mass that has a uniform low echogenicity lacking internal septation, with no acoustic enhancement or motion.18,19 This echogenicity probably is due to the accumulation of cellular material as well as cholesterol within the cyst lumen. Other sonographic reports have noted echogenicity in only the gravity-dependent portions of the cysts.18
The use of FNA has been mentioned in the literature as being effective in narrowing the diagnosis when a lateral neck lesion is present. Aspirate appears as a straw-colored fluid that microscopically may exhibit squamous cells, polymorphonuclear cells, lymphocytes and cholesterol crystals. Burgess and colleagues20 conducted a study from which they determined that squamous-cell carcinoma could be recognized on FNA by observing an increased cellular nuclear/cytoplasmic ratio, irregularity of nuclear outline and nuclear hyperchromatism.
Branchial cleft cysts, on the other hand, exhibit benign squamous cells and mild nuclear atypia. Many researchers and clinicians believe that FNA can be an important adjunct to clinical diagnosis of lateral neck lesions, especially when attempting to categorize the swelling as benign or malignant. In addition, the procedure is quick and findings typically are available in a matter of hours rather than days. However, FNA is not a substitute for thorough, microscopic examination of the lesion.
Although FNA may result in a decrease in mass size, this improvement is temporary and is no substitute for excision of the cyst. Moreover, it can be difficult for a cytopathologist to distinguish a well-differentiated (that is, low grade) metastatic deposit of squamous cells from a benign lesion such as a branchial cleft cyst. This represents a potential pitfall for those who rely on cytologic results alone.20 Branchial cleft cysts may have the ability to become malignant.21–23 To date, though, there has been no report of such an occurrence. Because of their lymphoid nature, these cysts can be confused with a metastatic lymph node or a primary malignancy from the thyroid gland.21–23
Surgical excision of the branchial cleft cyst is the treatment of choice and is considered definitive.
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TREATMENT
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Surgical excision of the branchial cleft cyst is the treatment of choice and is considered definitive.4,24 Some controversy exists about when to operate and whether every cyst requires removal. Many surgeons believe that presence of the lesion is reason enough for removal, primarily because of its propensity for infection.7 Excision of an asymptomatic lesion precludes or minimizes the chance of infection complicating a later surgery.
Any existing infection must be controlled before surgery can be performed, and can be achieved with antibiotics, with or without incision and drainage. Although incision and drainage may be necessary to treat an infective episode before surgery, it is not recommended as definitive treatment.24 Furthermore, some authors have suggested that complete drainage of lumenal contents before surgery is not desirable because this may make dissection more difficult.6,24 Infection doubles the recurrence rate of these anomalies,12 as do incomplete dissections and non-curative procedures.
Approximately 80 percent of branchial sinuses will open to the skin, and fewer will open to the pharynx. These sinuses initially may suggest a cyst, but on surgical exploration prove to be sinuses with a tract leading medially. Clinicians must take care to remove the entire tract to decrease the chance of recurrence. In particular, involvement of the deep aspect of the auditory canal has been attributed to an increased recurrence rate.24
Surgical complications include injury to surrounding structures such as the carotid sheath and the spinal accessory and hypoglossal nerves.16 Other treatment modalities that have been reported are radiation therapy, repeated incision and drainage, and use of sclerosing agents.16,17,24 These are considered noncurative, and if performed before surgery can increase the recurrence rate after surgical excision.12
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CASE REPORT
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A 32-year-old man visited the oral and maxillofacial surgery clinic at the University of Michigan Medical Center, Ann Arbor, with a history of swelling that had gradually increased in size during the previous five months (Figure 1
). The patient had no history of any previous swelling or infection within the head and neck region. His family’s medical history was negative for developmental swellings.
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ABSTRACT
SOURCE OF BRANCHIAL CYSTS
