Congenital neck masses may include thyroglossal duct cysts, dermoid cysts, lymphangiomas, branchial cleft cysts, teratomas or congenital muscular torticollis. Vascular processes such as venous malformations and hemangiomas are also often included in this category but will not be discussed here.
Thyroglossal duct cysts are the most common midline neck mass and second most common overall neck mass after benign lymphadenopathy. They are responsible for 70% of all congenital neck lesions. The thyroglossal duct forms as the thyroid diverticulum descends from the floor of the pharynx to eventually form the thyroid gland in the anterior neck. While the duct typically obliterates, any persistence of the duct along it’s path of descent can lead to a thyroglossal duct cyst. The cysts can occur anywhere near the central portion of the hyoid bone. The lesions may present in children or in adolescence as painless midline masses that elevate with swallowing or tongue protrusion. Part of the workup of thyroglossal duct cysts should include an ultrasound to evaluate its structure and confirm that normal thyroid tissue exists in the neck. The cysts can become infected with or without fistula formation and would require antibiotics or needle aspiration to treat. Definitive management of the cysts requires a Sistrunk procedure which involves complete excision of the cyst with the central 2/3 of the hyoid bone and tract leading to the base of tongue. Incomplete resection is a common cause of recurrence.
Dermoid cysts are the second most common midline neck mass and unlike thyroglossal duct cysts, they do not elevate with swallowing since these lesions are only attached to the dermis. Cervical dermoid cysts are comprised of ectodermal and mesodermal germ cell layers and may contain epithelial appendages such as hair or sebaceous glands. These masses do not get infected but because of their potential for enlargement, surgical excision is recommended. Teratomas differ from dermoid cysts in that they are composed of all three germ layers: ectoderm, mesoderm, and endoderm and are typically much larger. Cervical teratomas are present at birth and are often detected in utero, necessitating careful planning for a safe delivery due to potential airway obstruction. CT or MRI is the imaging modality of choice and surgical resection is mandatory.
Lymphatic malformations (cystic hygroma) are congenital malformations formed from blocked lymphatic ducts that fail to drain into the venous system. This results in multiple dilated sacs of lymph fluid. Up to 70% are present at birth and most are evident by 2 years of age. These masses are soft, compressible, non-tender and may extend to any neck level. They can be best evaluated by CT or MRI. Treatment consists of observation, injection of sclerosing agents, or surgical resection. Surgical resection is recommended in the presence of airway compromise, or significant cosmetic deformity. Recurrence rate is high even following surgical resection.
Branchial cleft abnormalities lead to up to 30% of all congenital neck masses. The anomalies are a result of disturbances in the development of the branchial apparatus. There are five branchial arches comprised of ectoderm, endoderm , and mesoderm which give rise to many of the structures in the head and neck. Clefts arise from ectoderm between each arch and typically obliterate through development, however the failure of these clefts to obliterate leads to cysts, sinuses, or fistulas. First branchial cysts are classified as type I and type II. Type I lesions are duplications of the external auditory canal and may present as fistulas inferior to the earlobe, but rarely as cystic masses. Type II lesions may present as cystic masses inferior to the the angle of the mandible and anterior to the sternocleidomastoid (SCM) muscle. Second branchial cleft cysts are the most common, comprising more than 90% of all anomalies and present as masses along the anterior border of the SCM. These lesions may not present until late childhood or adolescence. They can also become infected with oral flora since many have tracts that lead to the tonsillar fossa in the oropharynx. Type III and IV branchial cleft cysts are rare but present as neck swellings at the lower anterior border of the SCM or as recurrent thyroid abscesses since they both intimately associated with the thyroid gland. Many of these lesions have sinus tracts that open near the piriform sinus near the larynx. The definitive treatment for all branchial cleft anomalies is surgical excision including all fistula tracts. Cauterization of tracts near the piriform sinus has been shown as an effective treatment to prevent recurrent neck infections in type III/IV brachial cleft anomalies.