During fetal development, the thyroid gland starts at the base of the tongue. From here it gradually travels down the neck to its final position in front of the trachea, beneath the larynx. It leaves a track behind called the thyroglossal duct, which then disappears. When part of the thyroglossal duct persists it can give rise to a fluid filled cyst. This is called a thyroglossal cyst.
Ectopic thyroid tissue is a key differential diagnosis, as this commonly occurs at a similar location.
The main complication is infection of the cyst, causing a hot, tender and painful lump.
Thyroglossal cysts usually occur in the midline of the neck. They are:
Thyroglossal cysts move up and down with movement of the tongue. This is a key feature that demonstrates a midline neck lump is a thyroglossal cyst. This occurs due to the connection between the thyroglossal duct and the base of the tongue.
TOM TIP: Remember the key feature of thyroglossal cysts moving with movement of the tongue. This is a unique fact examiners like to use to test your knowledge. Look out for a thyroglossal cyst as a differential of a neck lump in your MCQ exam. If you come across a midline neck lump in a young child in your OSCEs, ask them to stick their tongue out and look for the lump moving upwards.
Ultrasound or CT scan can confirm the diagnosis.
Thyroglossal cysts are usually surgically removed to provide confirmation of the diagnosis on histology and prevent infections. The cyst can reoccur after surgery unless the full thyroglossal duct is removed.
Last updated January 2020