Thyroglossal duct cyst: the midline neck lump that rises when the tongue is stuck out
A thyroglossal (thyroid-to-tongue) duct cyst is a midline neck lump, usually painless, that is a fluid-filled leftover of the thyroid's path and rises when the tongue is stuck out.
Remember
Think of a thyroglossal duct cyst when a midline lump in the neck, usually painless, rises as the tongue is stuck out. It is a leftover of the path the thyroid took from the tongue, and rising on swallowing alone does not separate it from a thyroid swelling.
Memory aid
tongue out, cyst up
Stick the tongue out and watch the cyst lift, because the duct ties it to the tongue base.
A thyroglossal duct cyst is a congenital (present from birth) fluid-filled sac in the midline of the neck. Thyroglossal joins thyro- for thyroid and -glossal for tongue.
The cyst's origin lies in the embryo. The thyroid gland begins at the base of the tongue and descends to the front of the neck, leaving a thin path behind it called the thyroglossal duct. The duct normally closes and disappears. If part of it stays open, it can fill with fluid and form a cyst.
The cyst stays connected to the tongue base through the remnant of the duct. So sticking the tongue out pulls the cyst upwards. To test this, ask the patient to stick out their tongue while you feel the lump. The cyst can also rise on swallowing, so swallowing alone does not separate it from a thyroid swelling, which moves because the thyroid is attached to the trachea (windpipe).
The cyst is usually painless, but if its fluid becomes infected it can become painful. It is usually found in childhood, but it can first be noticed in adults.
Treatment is surgical removal of the cyst and the entire duct (the Sistrunk procedure), which usually includes the central part of the hyoid bone (a small U-shaped bone above the voice box) to reduce the chance of recurrence.
Position and movement together separate it from these lumps:
- A goitre (an enlarged thyroid gland) rises on swallowing but not on tongue protrusion.
- A branchial cleft cyst (a congenital cyst from embryonic branchial cleft tissue) lies at the side of the neck.
- A dermoid cyst (a pocket of trapped skin-forming tissue) is also a painless midline lump, but it has no duct to the tongue base.
Key facts
- Sign
- a midline neck lump that rises when the tongue is stuck out; it may also rise on swallowing.
- Cause
- part of the thyroglossal duct, the path the thyroid took from the tongue base, fails to close.
- Thyroid contrast
- a thyroid swelling rises on swallowing, whereas the tongue sign points to the cyst.
- Pain
- usually painless, but infection can make the cyst painful.
- Age
- usually found in childhood, but it can first be noticed in adults.
- Treatment
- surgical removal of the cyst and the whole duct, usually with the central part of the hyoid bone, to reduce recurrence.
Exam traps
- A goitre rises on swallowing, but swallowing alone does not separate it from a thyroglossal duct cyst, which can also rise on swallowing. The tongue test is the useful one.
- A dermoid cyst is also a painless midline lump, often beneath the chin, but it is trapped skin-forming tissue and not part of the path from the tongue to the thyroid, so it does not characteristically rise when the tongue is stuck out.
- A branchial cleft cyst is also a painless congenital cyst, but it sits at the side of the neck, typically in front of the sternocleidomastoid muscle (the large muscle running up the side of the neck), rather than in the midline, and it is not tied to the tongue by a duct.
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