A 33-year-old woman presented with an asymptomatic lesion on the neck (see the accompanying figure). The lesion had been present for 15 years, and the patient was otherwise in good health. The physical examination revealed a firm, subcutaneous nodule that measured 1 cm on the midline of the anterior neck.
The correct answer is E: thyroglossal duct cyst. The thyroglossal duct cyst is the most common congenital neck mass. It results from the incomplete obliteration of remnants of an epithelial tract formed during migration of the thyroid during embryo genesis. Some of these lesions do not present until adulthood.
Although ectopic thyroid tissue is rare, it most commonly presents in the anterior cervical area in the region of the thyroglossal duct.1 A preoperative thyroid scan should be performed to rule out ectopic thyroid tissue.
Besides ectopic thyroid tissue, the differential diagnosis of an anterior neck mass includes epidermal cyst, branchial cleft cyst and dermoid cyst. Although an epidermal cyst may occur on any hair-bearing skin, the midline presentation necessitates consideration of a congenital anomaly. Branchial cleft cysts can form in any of the embryologic branchial clefts of the anterior neck. Most commonly the second branchial cleft is involved, and it presents as a small nodule located laterally near the anterior border of the sternocleidomastoid muscle. They can occasionally become quite large and tender when infected, necessitating surgical removal.
Dermoid cysts are congenital cysts that commonly occur on the temple and may occur on the anterior neck. Histopathologic examination shows a lining of epidermis with various mature epidermal appendages, including hair follicles with hairs that project into the lumen, sebaceous glands and apocrine glands. Dermoid cysts result from entrapment of skin along lines of embryonic closure.2
Approximately 7 percent of the population may have some thyroglossal duct remnants.3 The cyst can appear anywhere from the base of the tongue to the level of the larynx. A pathognomic sign for a thyroglossal duct cyst is vertical movement of the mass on swallowing. Thyroglossal duct cyst carcinoma is rare and is more common in adults. The treatment of choice for thyroglossal duct cyst is excision using a procedure in which the central portion of the hyoid bone is removed along the cyst tract to the base of the tongue.4 Simple excision of the cyst often leads to recurrence.