Thyroglossal duct cyst – causes, symptoms, diagnosis, treatment, pathology

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. Now, normally during fetal development, a
tiny depression, called the foramen cecum, forms at a spot between the front two-thirds
and the back one-third of the tongue. The tissue underlying the foramen cecum is
different than the rest of the tongue, and it’s cells develop into the thyroid gland. 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 thyroid gland descends down past the base
of the tongue and the hyoid bone, which is a small bone present below the chin, before
finally settles down in front of the trachea, in the neck. 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 the
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. Now, these can also form if the thyroglossal
duct cyst is damaged during surgery. Third, in some people, the thyroid gland cells
remain in the thyroglossal duct and don’t descend down. If that happens, a thyroid gland may not develop
normally. And, in addition, very rarely a thyroid tumor
might develop in the cyst, since there are still thyroid cells in the walls of the cyst. The most common symptom of a thyroglossal
duct cyst is painless swelling in front of the neck, which can lie anywhere along the
path of the thyroglossal duct. Usually its midline or just slightly off of
the midline, and the most common locations is subhyoid, just below the hyoid bone, and
suprahyoid, just above the hyoid bone. Because of its connected to the tongue, the
thyroglossal duct cyst moves up when a person swallows or sticks out their tongue. Also, the cyst might appear red and be painful
If the cyst gets infected. The diagnosis of a thyroglossal duct cyst
is usually done with an imaging study like an ultrasound or CT scan, and confirmed with
fine needle aspiration. Sometimes a thyroid function test is done,
to assess whether a person has a healthy thyroid gland. Treatment of a thyroglossal duct cyst is surgical
removal of the entire thyroglossal tract. In addition, antibiotics may be used to treat
infections. All right, as a quick recap, as the thyroid
gland descends during development a tiny thyroglossal duct forms. If the thyroglossal duct doesn’t close in
on itself, it can start to fill up with mucus which creates cysts anywhere along its tract. These cysts are usually midline on the neck,
just above or below the hyoid bone, and can be surgically removed.

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