A branchial cleft cyst is a congenital neck mass characterized by a fluid-filled sac. This anomaly typically develops under the skin on one side of the neck, between the jaw and the collarbone. Branchial cleft cysts are benign and are one of the most common causes of neck masses present at birth. They may remain unnoticed for many years and only become apparent if they become infected.
Formation During Fetal Development
Branchial cleft cysts result from incomplete tissue development during the early stages of fetal formation. This occurs around the fourth to seventh week of gestation, when five basic structures known as branchial arches begin to form the face and neck. The arches are separated by external grooves called clefts and internal grooves called pouches.
Normally, these clefts and pouches disappear completely as the surrounding tissues fuse together. If a portion of this tissue fails to involute fully, it becomes trapped, creating an epithelial-lined pocket. This trapped remnant fills with fluid, resulting in a branchial cleft cyst.
The underlying cause is developmental, not a result of illness or injury after birth. The majority of these anomalies stem from the second branchial arch, leading to the most common type of cyst.
Recognizing the Symptoms and Location
The most typical presentation of a branchial cleft cyst is as a small, soft, and usually painless lump or swelling in the neck. Although present from birth, the mass often becomes noticeable in childhood or early adulthood, sometimes enlarging following an upper respiratory tract infection. The cyst may also present with a small opening on the neck that drains mucous-like fluid, known as a sinus tract.
The location depends on which branchial arch failed to close, categorizing the anomalies into four types. Second branchial cleft cysts are the most common, accounting for up to 95% of cases, and appear along the front edge of the sternocleidomastoid muscle. First branchial cleft cysts are less common and are typically found near the ear or just below the jawline.
Third and fourth branchial cleft cysts are the least frequent types, often appearing lower in the neck, sometimes near the thyroid gland. If a cyst becomes infected, it may become tender, red, and swollen, occasionally forming an abscess. In rare instances, a very large cyst can cause compressive symptoms like difficulty swallowing or noisy breathing.
Diagnosis and Medical Intervention
Diagnosis typically begins with a thorough physical examination and a review of the patient’s medical history. Imaging studies are often used to confirm the diagnosis and distinguish the cyst from other possible neck masses. An ultrasound is frequently the initial tool, but a CT scan or MRI scan may be necessary to define the cyst’s exact size and location before surgical planning.
The definitive treatment for a branchial cleft cyst is complete surgical excision. This procedure is recommended to prevent recurrent infections and abscess formation, which are common complications of an untreated cyst. Surgery involves removing the entire cyst and any associated tract or sinus to minimize the chance of the anomaly returning.
Before surgery, any active infection must be managed with antibiotics and sometimes drainage to lower the risk of complications. The prognosis following complete surgical removal is generally excellent. A small percentage of cases may experience recurrence if any part of the tract is left behind.