A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 4-year-old girl is brought to the physician for a painless lump on her neck. She has no history of serious illness and her vital signs are within normal limits. On examination, there is a firm, 2-cm swelling at the midline just below the level of the hyoid bone. The mass moves cranially when she is asked to protrude her tongue. Which of the following is the most likely diagnosis?
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A
Thyroglossal cystCorrect. A midline, firm neck mass just below the hyoid bone that elevates with tongue protrusion is the diagnostic presentation of a thyroglossal duct cyst.
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B
LaryngoceleIncorrect. A laryngocele is an air-filled saccular outpouching of the laryngeal ventricle; it enlarges with Valsalva, is more common in adults (especially glassblowers), and does not move with tongue protrusion.
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C
Cystic hygromaIncorrect. A cystic hygroma is a lymphatic malformation in the posterior cervical triangle, soft and transilluminating, usually present at birth — not a firm midline mass that moves with the tongue.
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D
Dermoid cystIncorrect. Dermoid cysts of the neck are midline but do not move with tongue protrusion because they are not tethered to the hyoid or foramen cecum.
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E
Branchial cleft cystIncorrect. Branchial cleft cysts are lateral neck masses along the anterior border of the sternocleidomastoid, not midline; they do not elevate with tongue protrusion.
↑ Tap an answer to reveal the reasoning
Answer: A. A young child with a painless, firm, midline neck mass located just below the hyoid bone that elevates with tongue protrusion has a thyroglossal duct cyst. Embryologically, the thyroid gland originates at the foramen cecum of the tongue and descends through the floor of the pharynx to its adult pretracheal position, passing in front of (and tightly associated with) the developing hyoid bone. The thyroglossal duct normally involutes; persistence of any portion results in a thyroglossal duct cyst. Because the cyst is tethered through the hyoid to the foramen cecum, the entire complex elevates with tongue protrusion — a pathognomonic physical finding.
Thyroglossal duct cysts are the most common congenital midline neck mass in children. They are typically firm, painless, and rubbery, located at the level of the hyoid (75% are at or below the hyoid). Preoperative evaluation should include a thyroid ultrasound to confirm the presence of a normally located thyroid gland (occasionally the cyst contains the only functional thyroid tissue — ectopic thyroid — and removal would render the patient athyroid). Definitive treatment is the Sistrunk procedure: excision of the cyst, the tract, the central portion of the hyoid bone, and a core of tissue up to the foramen cecum.
The alternatives are anatomically wrong. A laryngocele is an air-filled dilation of the laryngeal saccule that protrudes through the thyrohyoid membrane; it enlarges with Valsalva, not tongue protrusion, and is uncommon in children. A cystic hygroma is a lymphatic malformation, usually in the posterior cervical triangle, soft and transilluminating, often present at birth and frequently very large. A dermoid cyst is a midline neck or scalp mass containing ectodermal elements (hair, sebum, keratin) but does not move with tongue protrusion.
Clinical pearl: midline + below hyoid + moves with tongue protrusion = thyroglossal duct cyst; lateral neck cyst along the anterior border of the SCM = branchial cleft cyst.
**Why each option:**
**A.** Correct. A midline, firm neck mass just below the hyoid bone that elevates with tongue protrusion is the diagnostic presentation of a thyroglossal duct cyst.
**B.** A laryngocele is an air-filled saccular outpouching of the laryngeal ventricle; it enlarges with Valsalva, is more common in adults (especially glassblowers), and does not move with tongue protrusion.
**C.** A cystic hygroma is a lymphatic malformation in the posterior cervical triangle, soft and transilluminating, usually present at birth — not a firm midline mass that moves with the tongue.
**D.** Dermoid cysts of the neck are midline but do not move with tongue protrusion because they are not tethered to the hyoid or foramen cecum.