A 23-year-old male patient presents with midline swelling in the neck. The swelling moves with deglutition and protrusion of the tongue. What is the likely diagnosis?

Correct Answer: C. Thyroglossal cyst

The thyroglossal cyst is the most common congenital neck mass (70% of all congenital neck lesions in Indian populations). The discriminating clinical features here are: (1) midline location, (2) movement with deglutition (upward movement on swallowing), and (3) movement with tongue protrusion (upward movement when tongue is protruded). These pathognomonic signs arise because the thyroglossal cyst develops along the embryologic path of thyroid descent—the thyroglossal duct—which runs from the foramen caecum at the base of tongue, through the midline of the neck, to the lower pole of the thyroid. The duct normally obliterates by 8–10 weeks of gestation; failure of complete obliteration leaves remnants that can form cysts. The cyst is lined with stratified squamous epithelium and may contain thyroid follicles. Movement with swallowing and tongue protrusion occurs because the cyst is tethered to the hyoid bone and tongue base via the remnant duct. This is the classic presentation in a young adult. Treatment is Sistrunk's operation (en bloc excision of the cyst, tract, and central portion of the hyoid bone), which reduces recurrence from ~50% (simple excision) to <5%. Bailey & Love Ch. 37

Why the other options are wrong

A. Brachial cyst — Brachial cysts arise from remnants of the second branchial cleft and present as lateral neck masses (anterior to sternocleidomastoid), not midline. They do NOT move with deglutition or tongue protrusion—they are fixed to surrounding tissues. Brachial cysts are the second most common congenital neck mass but the clinical location and movement pattern are entirely different, making this a common distractor for students who know branchial anatomy but miss the midline clue. B. Plunging ranula — A ranula is a cyst of the sublingual salivary gland (Wharton's duct) that presents as a floor-of-mouth swelling (sublingual, not midline neck). A plunging ranula extends into the neck but still originates from the sublingual gland and presents with intraoral swelling first. It does NOT show the characteristic movement with tongue protrusion seen in thyroglossal cysts. The age and presentation (pure neck swelling without oral component) rule this out. D. Dermoid cyst — Dermoid cysts are midline masses but they are fixed and immobile—they do NOT move with deglutition or tongue protrusion because they are not tethered to the hyoid bone or tongue base. Dermoid cysts contain hair, sebaceous material, and sweat glands (ectodermal remnants), whereas thyroglossal cysts contain thyroid tissue. The absence of movement with swallowing and tongue protrusion is the key discriminator, though both can be midline.

High-Yield Facts

Mnemonics

MIDLINE MOVES = Thyroglossal Midline location + Increases with Deglutition + Lifts with Inflation (tongue protrusion) + Neck mass + E = Move with Oral maneuvers + Vertical Extent (foramen caecum to thyroid) = Thyroglossal cyst. Use when you see midline + movement with swallowing/tongue protrusion. SISTRUNK = Hyoid + Duct + Cyst Sistrunk's operation removes the cyst, the entire tract, AND the central portion of the hyoid bone en bloc. Remember: Sistrunk = Systematic removal of Structures (cyst + tract + hyoid). This is the gold standard to prevent recurrence.

NBE Trap

NBE often pairs thyroglossal cyst with other midline neck masses (dermoid, epidermoid) to test whether students rely on the movement with deglutition and tongue protrusion as the discriminating feature. Students who only remember "midline" without the pathognomonic movement pattern may incorrectly choose dermoid cyst.

Clinical Pearl

In Indian clinical practice, thyroglossal cysts are often discovered incidentally during routine neck examination or when patients present with infection/abscess formation. A simple bedside test—asking the patient to swallow or protrude the tongue while palpating the midline neck mass—confirms the diagnosis and guides referral to a surgeon for Sistrunk's operation, which is the standard of care in most Indian tertiary centers.

_Reference: Bailey & Love Ch. 37 (Thyroid and Parathyroid); Robbins Ch. 8 (Congenital Anomalies)_