Thyroglossal Cysts

Question 1

Define thyroglossal cyst

Answer 1

An epithelium-lined cyst found along the course of descent of the thyroid gland.

Question 2

What are the cause/risk factors of thyroglossal cysts?

Answer 2

• The thyroglossal duct is a tract of embryonic mesoderm that originates between the 1st and 2nd branchial pouches, represented by the foramen caecum of the tongue.
• It descends to a pretrachael site during development to form the thyroid gland.
• The duct normally disappears in the 6th week; however, if some tissue remains at any point along its course, it may develop into a cyst.

Risk Factors:
• 1–2% of cases are associated with lingual or ectopic thyroid tissue.
• Very rare familial variants (mostly autosomal dominant in prepubertal girls).

Question 3

What are the symptoms of thyroglossal cysts?

Answer 3

• A swelling or lump is noticed in the midline of the anterior neck (90%)
• 10% can be lateral, with 95% of these on the left side.
• Mostly asymptomatic, but in 5% cases there may be tenderness or rapid enlargement due to infection.

Question 4

What are the signs of thyroglossal cysts?

Answer 4

• Midline smooth rounded swelling, typically between the thyroid notch and hyoid bone, although sometimes found in the submental region.
• Moves upwards on protrusion of the tongue and with swallowing.
• Can usually be transilluminated.
• Differential diagnosis: Lymph node, epidermal inclusion (dermoid) cysts, salivary duct abnormality or ectopic thyroid tissue.

Question 5

What investigations are carried out for thyroglossal cysts?

Answer 5

• None may be necessary in a euthyroid patient.
• If the cyst is suprahyoid, thyroid function tests and an isotope (99Tc) should be carried out to exclude a lingual thyroid, as its removal may render the patient hypothyroid.
• Ultrasound or MRI scan: To differentiate from other structures (cysts have a high signal on T2 weighting).