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Summary Table

Category	Detail
Risk Factors	Children and young adults (most common pediatric midline neck mass); no significant sex predilection
Etiology	Failure of obliteration of the thyroglossal duct after embryologic descent of the thyroid gland from the foramen cecum to its pretracheal position
Patient Presentation	Painless, midline anterior neck mass; may become tender if secondarily infected
Classic Physical Exam	Smooth, well-circumscribed midline mass that elevates with tongue protrusion and swallowing
Key Diagnostic Results	Ultrasound (best initial test) shows a well-defined cystic lesion in the midline; thyroid ultrasound confirms functioning thyroid tissue is present elsewhere; fine-needle aspiration if diagnosis is uncertain
Management	Sistrunk procedure (excision of the cyst, the entire thyroglossal duct tract, and the central portion of the hyoid bone)
Keywords	"Midline neck mass," "moves with tongue protrusion," "moves with swallowing," "child with anterior neck lump," "foramen cecum"

1. Pathophysiology

During embryologic development, the thyroid gland originates at the foramen cecum at the base of the tongue. It then descends along a midline tract, passing anterior to (and intimately associated with) the hyoid bone, to reach its final pretracheal position by the seventh week of gestation. This migration path is known as the thyroglossal duct. Normally, this duct degenerates and disappears completely by the tenth week.

When the duct fails to obliterate, residual epithelial cells along the tract can accumulate secretions and form a thyroglossal duct cyst. Because the tract is tethered superiorly to the foramen cecum at the tongue base and inferiorly to the thyroid, the cyst maintains a physical connection to both structures. This is why the hallmark exam finding is elevation of the mass with tongue protrusion: the tongue base pulls the residual tract (and the cyst attached to it) upward. Similarly, the cyst moves with swallowing because of its attachment to the hyoid bone and pretracheal structures.

In some patients, the cyst contains ectopic thyroid tissue within its wall. This is clinically important for two reasons. First, rarely, this ectopic tissue may represent the only functioning thyroid tissue in the body. Removing it without confirming the presence of a normal thyroid gland could render the patient permanently hypothyroid. Second, ectopic thyroid tissue within the cyst wall carries a small risk of malignant transformation, most commonly papillary thyroid carcinoma.

Secondary infection of the cyst (often following an upper respiratory tract infection) can cause it to become erythematous, tender, and enlarged, mimicking an abscess. This is a common clinical scenario on the exam: a child with a previously noted painless midline lump now presents with a painful, swollen neck mass after a recent URI.

2. Classification and Clinical Manifestation

Location Along the Tract	Relative Frequency	Clinical Features
Suprahyoid (between foramen cecum and hyoid)	~20-25%	Located in the submental region; may be confused with a dermoid cyst or sublingual mass
At the level of the hyoid bone	~15-20%	Intimately associated with the hyoid body; firm on palpation due to bony proximity
Infrahyoid (between hyoid and thyroid gland)	~50-65% (most common)	Classic midline mass overlying the thyrohyoid membrane or strap muscles; the textbook presentation
Intralingual (at foramen cecum)	Rare	Presents as a posterior tongue mass; may cause dysphagia or airway compromise in neonates

Regardless of location, the unifying feature is that the mass sits in or very near the midline and demonstrates movement with tongue protrusion. An off-midline neck mass should prompt consideration of other diagnoses such as branchial cleft cyst (lateral) or cystic hygroma (posterior triangle).

3. Diagnostic Workup

Test	Role	Key Findings
Ultrasound of the neck mass	Best initial test	Well-defined, anechoic or hypoechoic cystic structure in the anterior midline; may contain internal debris if infected
Thyroid ultrasound	Mandatory before surgical excision	Confirms the presence of a normal thyroid gland in its usual pretracheal location
Fine-needle aspiration (FNA)	If there is concern for malignancy or the diagnosis is uncertain	May reveal benign cyst contents; if solid component is present, evaluate for papillary thyroid carcinoma
CT or MRI	Rarely needed; used for complex or recurrent cases	Delineates the full extent of the tract, relationship to the hyoid bone, and involvement of surrounding structures
Thyroid function tests (TSH, free T4)	Adjunctive if ectopic thyroid is suspected	Usually normal; abnormal values suggest the cyst may contain the only functioning thyroid tissue

The diagnostic approach begins with ultrasound, which is non-invasive, inexpensive, and reliably characterizes the cystic nature and midline location of the mass. The most critical step that students frequently overlook is the thyroid ultrasound. Before any surgical intervention, you must confirm that a normal thyroid gland exists in its expected position. If the only thyroid tissue in the body is within the cyst, excision would cause permanent hypothyroidism. On the exam, a question that describes a midline mass with no visible thyroid on imaging is testing whether you recognize the possibility of an ectopic thyroid (lingual thyroid) presenting as a "thyroglossal duct cyst."

If the ultrasound reveals a predominantly solid component or if FNA cytology returns follicular cells with nuclear features concerning for malignancy, the workup should escalate to rule out papillary thyroid carcinoma arising within the cyst. This occurs in approximately 1% of thyroglossal duct cysts and is the most common malignancy found in this setting.

CT or MRI is generally reserved for cases where recurrence has occurred after initial surgery, or when the anatomic relationship between the tract and the hyoid bone needs to be mapped in greater detail.

4. Management and Treatment

Clinical Scenario	Management	Details
Uncomplicated cyst	Sistrunk procedure	Excision of the cyst, the entire thyroglossal duct remnant, and the central portion of the hyoid bone, with dissection up to the foramen cecum
Infected cyst (acute)	Antibiotics first, then Sistrunk procedure	Treat the infection with oral or IV antibiotics (covering skin flora); if an abscess forms, incision and drainage may be needed; definitive excision is performed after the infection resolves
Papillary carcinoma within the cyst	Sistrunk procedure + total thyroidectomy + radioactive iodine (if indicated)	Managed similarly to primary papillary thyroid carcinoma; Sistrunk alone is insufficient if malignancy is found
Ectopic thyroid only (no normal thyroid gland)	Do NOT excise; consider thyroid hormone supplementation	If the cyst is the only thyroid tissue, removal causes permanent hypothyroidism; manage conservatively or with levothyroxine

The Sistrunk procedure is the gold standard and the most commonly tested treatment. Simple cyst excision alone (without removing the central hyoid and tract up to the foramen cecum) has a recurrence rate of approximately 50%. The Sistrunk procedure drops recurrence to under 5% because it removes the entire embryologic pathway along which residual epithelium may persist.

The key steps of the Sistrunk procedure are: excision of the cyst itself, removal of the central body of the hyoid bone (because the duct passes through or intimately contacts it), and coring out the tract tissue all the way up to the foramen cecum at the base of the tongue. On the exam, the test-writer may present a scenario of a recurrent thyroglossal duct cyst and ask what went wrong: the answer is almost always that only simple excision was performed without removing the hyoid and the full tract.

For infected cysts, the principle is do not operate on an actively infected field. Treat the infection first, let it cool down, and then proceed with definitive surgery. If an abscess has formed, drain it, but do not attempt the full Sistrunk procedure in the acute setting because tissue planes are obscured and the risk of incomplete excision (and therefore recurrence) is high.

5. Differential Diagnosis and Distractors

Differential Diagnosis	Why It Is Similar	Key Discriminator
Dermoid cyst	Also a painless midline neck mass in a child; may be submental	Does not move with tongue protrusion; located superficially in the subcutaneous tissue, not deep to the strap muscles; no connection to the hyoid
Ectopic (lingual) thyroid	Midline mass; related to thyroid embryology; may elevate with swallowing	Located at the base of the tongue (posterior), not in the anterior neck; presents with dysphagia or muffled voice; thyroid scan shows uptake only at the tongue base with no pretracheal thyroid
Branchial cleft cyst	Neck mass in a child or young adult; can become infected	Located laterally, along the anterior border of the sternocleidomastoid; does not move with tongue protrusion
Cystic hygroma (lymphatic malformation)	Cystic neck mass in a child; painless; transilluminates	Located in the posterior triangle of the neck; soft, compressible, brilliantly transilluminant; does not move with tongue protrusion
Reactive lymphadenopathy	Neck mass in a child; may be tender if infected	Usually lateral, multiple, and mobile; associated with recent infection; no midline fixation or movement with tongue protrusion
Thyroid nodule	Anterior neck mass that moves with swallowing	Located within the thyroid gland itself (lower anterior neck); does not move with tongue protrusion; ultrasound shows an intrathyroidal lesion

The single most reliable discriminator for thyroglossal duct cyst on the exam is elevation of the mass with tongue protrusion. No other common pediatric neck mass behaves this way. If the vignette includes this finding, the answer is thyroglossal duct cyst regardless of other details.

6. Traps and High-Yield Pearls

The most common way students lose points on thyroglossal duct cyst questions is by selecting simple excision instead of the Sistrunk procedure. The exam tests whether you understand that the entire tract, including the central hyoid bone, must be removed to prevent recurrence. If you see a recurrent midline neck mass after surgery, the "next best step" is revision surgery using the Sistrunk technique.

The second major trap involves the scenario where imaging reveals no thyroid gland in the pretracheal position. Students who jump to excision without first confirming the presence of a normal thyroid will select the wrong answer. The correct response is to obtain a thyroid scan (or at minimum, confirm via ultrasound) to determine whether the midline mass is actually the patient's only thyroid tissue. Excision in that setting is contraindicated.

A third pearl: when a question stem describes a thyroglossal duct cyst with a solid component or unexpected pathology on FNA, the test-writer is leading you toward papillary thyroid carcinoma arising within the cyst. The management then shifts from Sistrunk alone to Sistrunk plus total thyroidectomy.

Finally, remember the embryology anchor. The thyroid descends from the foramen cecum, passes through the hyoid, and lands in the pretracheal space. Every clinical feature, every surgical step, and every exam question about this diagnosis traces back to that single developmental pathway.

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