Testing & Diagnosis for Thyroglossal Duct Cyst in Children

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How is a thyroglossal cyst diagnosed?

The diagnosis of a thyroglossal duct cyst can often be based on physical examination. Based upon its etiology, a thyroglossal duct cyst typically presents as a midline neck mass. The most common location is at or below the level of the hypoid bone, a palpable landmark under the jaw and above the voice box (larynx). The migration of the thyroid generally goes down the midline so the cyst remnants of this journey can occur at any point along this path. A significant number, as shown in the diagram, Thyroglossal image - figure 1occur centered around this hyoid bone. Classically, this cyst will be elevated in the neck if the patient either swallows or sticks their tongue out. Other entities can occur in the midline. A dermoid cyst is probably the most common entity in this location and it is formed when the two folds of the neck meet in the midline in the developing fetus. If there is some overlap in this union, the dermoid cyst which is lined by skin-like tissue occurs. These generally grow proportionally with the patient as they are developing and there is less motion with swallowing than with the thyroglossal duct cyst. You can also have swollen (hypertrophied) lymph nodes in the midline as well. The final entity, and the rarest that can appear in the midline of the neck, is the thyroid gland which has failed to migrate down to the lower portion of the neck where it would normally reside. If this is not apparent at birth as a larger mass, it may be only a segment of the thyroid which failed to descend.

Often a cervical ultrasound is performed to confirm that there is a normal thyroid gland in the lower neck. It is also used to evaluate the mass and can generally identify if the lump is due to swollen lymph nodes or is normal thyroid tissue. It is less able to differentiate between a
dermoid cyst and a thyroglossal duct cyst, but its appearance may lead to one or the other of these diagnoses.

If the mass presents as a red or tender swelling in the neck, then it is more likely to be an infected thyroglossal duct cyst, although dermoid cysts can become infected as well.

- Sandra L. Fenwick, President and CEO

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