Question:

A 6-year-old boy is brought to the office for evaluation of a neck lump. His mother first noticed the mass 2 weeks ago while he was experiencing cold symptoms. His nasal congestion and fever resolved within several days with symptomatic treatment, but the mass failed to improve. The patient was born at full term without pregnancy complications and has been healthy until now. He has received all recommended vaccines and takes no medications. The patient is afebrile, and height and weight are at the 60th percentile for his age. Physical examination shows a 1.5-cm, soft, mildly tender mass in the midline upper neck. It moves up and down when the patient swallows; there are no other neck masses. The nasal turbinates are pink with no rhinorrhea, and the tonsils are normal with no erythema or exudates. The remainder of the examination shows no abnormalities. Which of the following is the most likely underlying cause of this patient's condition?

Embryologic anomaly

Glandular duct obstruction

Granulomatous inflammation

Neoplastic proliferation

Reactive lymphadenopathy

Suppurative bacterial infection

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Thyroglossal duct cyst
Embryology	Forms along path of thyroid descent Foramen cecum (base of tongue) to base of anterior neck
Clinical presentation	Midline cystic neck mass Moves superiorly with swallowing or tongue protrusion Often present after upper respiratory tract infection (secondary infection) Associated with ectopic thyroid tissue
Management	Confirm presence of normal thyroid tissue Surgical resection of cyst, associated tract & central portion of hyoid bone

This patient with a midline neck mass that moves superiorly with swallowing has a thyroglossal duct cyst (TDC). A TDC is often detected when it becomes secondarily infected after an upper respiratory tract infection, leading to erythema and tenderness. It may also be noted incidentally.

The thyroid gland is formed as an outpouching from the pharyngeal epithelium at the base of the tongue. It then descends to the base of the anterior neck via the thyroglossal duct. If the duct fails to atrophy normally, a TDC can develop from the epithelial remnants within the duct, forming a midline, cystic mass. Because the tract connects to the base of the tongue, protrusion of the tongue or swallowing causes the TDC to move superiorly.

Due to the risk of recurrent infection, a TDC should be surgically removed. Because a TDC is associated with ectopic thyroid tissue and may be the only source of functioning thyroid tissue, thyroid imaging is required preoperatively.

(Choice B) Rarely, obstruction of the sublingual salivary gland duct can lead to pseudocyst (ranula). If it is large, the pseudocyst can extend from the floor of the mouth into the neck. However, it would be lateral (not midline) and would not move with swallowing.

(Choice C) In children, nontuberculous mycobacterial lymphadenitis can present as a neck mass. However, it is typically a slowly enlarging, lateral neck mass, with overlying violaceous discoloration of the skin.

(Choice D) Pediatric malignancies (eg, lymphoma) can often present as neck masses. However, they are typically lateral and do not move with swallowing.

(Choice E) Cervical reactive lymphadenopathy is very common in children and often presents as an enlarged neck mass following an upper respiratory tract infection. However, it is typically lateral, often involves multiple nodes, and does not move with swallowing.

(Choice F) Suppurative sialadenitis (salivary gland infection) can result in a swollen, tender neck mass. However, it would be firm, exquisitely tender, nonmobile with swallowing, and not located in the midline.

Educational objective:
In children, a midline, cystic neck mass that moves with swallowing is likely a thyroglossal duct cyst. A thyroglossal duct cyst forms from retained epithelium from the embryologic descent of the thyroid gland.