The differential diagnosis of neck masses can be categorized by the location of the mass itself; the most common categorization is between lateral and midline masses. The most frequent causes of lateral masses are lymphadenopathy, branchial cleft cyst malignancy, cystic lymphangioma, and dermoid and teratoid cysts. Although thyroglossal duct cysts are the most common cause of midline masses, the differential diagnosis also includes dermoid and teratoid cysts, ectopic thyroid tissue, cancer, and cystic lymphangiomas.
On radiologic imaging, thyroglossal duct cysts appear as a cystlike mass along the course of the thyroglossal duct. They must be differentiated from dermoid cysts and lymphangiomas. A dermoid cyst usually contains fat; lymphangioma is most common in infancy or early childhood, and it usually occurs in the posterior triangle of the neck, behind the sternocleidomastoid muscle.
A thyroglossal duct cyst must also be differentiated from an ectopic thyroid gland. If an ectopic thyroid gland is mistakenly removed, the patient may require long-term thyroid treatment for hypothyroidism. Often, patients with an ectopic thyroid gland also have hypothyroidism, and they have an elevated thyroid-stimulating hormone level.
Thyroglossal duct cysts are diagnosed on the basis of the clinical history and confirmed with diagnostic imaging. Most patients with thyroglossal duct cysts present with either a history of a slowly growing, asymptomatic mass or a relatively rapidly growing mass (if the cyst is infected) in the anterior midline of the neck. Frequently, the swelling is exacerbated during an upper respiratory infection. The pathognomonic sign of a thyroglossal duct cyst is that it moves with swallowing and with protrusion of the tongue; however, the mobility of larger cysts may be restricted.
Imaging studies, including ultrasound and CT of the neck, confirm the diagnosis and help to rule out a possible ectopic thyroid gland. Thyroid function tests should be obtained to confirm normal thyroid function.
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Cite this: Jitendra Gohil, Pramod Gupta. A 45-Year-Old Man With Gradual Neck Swelling - Medscape - Nov 30, 2016.