AssessmentsThyroglossal duct cyst
Thyroglossal duct cyst
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 17-year-old girl presents to the physician for evaluation of a neck mass. She first noticed the mass five weeks ago, following an upper respiratory infection. She has not experienced any dyspnea or dysphagia. Past medical history is unremarkable. Temperature is 37.5°C (99.5°F), blood pressure is 109/72 mmHg, and pulse is 68/min. On physical examination, a midline mass is observed over the anterior neck around 1 centimeter below the hyoid bone. The mass is soft and nontender to palpation. The mass moves when the patient swallows. Which of the following best describes the underlying cause of this patient’s condition?
Content Reviewers:Rishi Desai, MD, MPH
A thyroglossal duct cyst, sometimes just called a thyroglossal cyst, is a congenital disorder where the thyroglossal duct, which is a tiny canal connecting the thyroid gland with the tongue during fetal development, grows in size and fills up with mucus, which forms a cyst.
Through development, the thyroid gland tissue migrates downward as it grows, but it still stays connected by a tiny canal called the thyroglossal duct.
The walls of the thyroglossal duct are lined by lymphoid cells, as well as epithelial cells which secrete mucus into the cavity.
Normally, once the thyroid gland has reached its final resting position, it stretches out a bit and the walls of the thyroglossal duct stick to each other, obliterating the canal.
Over time the thyroglossal duct starts to disintegrate and by the third month of fetal development, the duct is usually gone.
In some people, though, the thyroglossal duct doesn’t close completely, and instead parts of it widen to form pockets, or cysts.
The cysts get filled with mucus secreted by the epithelial cells in its walls.
These mucus filled thyroglossal duct cysts stick around as the fetus develops, and then they can cause a few problems.
For example, when there’s an infection of the respiratory tract, it can easily spread to the thyroglossal duct cyst since there are lymphoid, aka immune cells in the walls of the cyst.
Local inflammation also stimulates the epithelial cells of the thyroglossal duct cyst to increase their secretions, and that makes the cyst grow in size.
Second, the thyroglossal duct cysts can enlarge to a point where it bursts open, letting the mucus pour out and that can form a discharging sinus, which is sometimes also referred to as a thyroglossal fistula, even though it’s usually not a true fistula.
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