Thyroglossal duct cyst

Thyroglossal duct cysts (TGDC) are the most common congenital neck cyst. They are typically located in the midline and are the most common midline neck mass in young patients. They can be diagnosed with multiple imaging modalities, including ultrasound, CT, and MRI.

Thyroglossal duct cysts typically present during childhood (90% before the age of 10), or remain asymptomatic until they become infected, in which case they can present at any time.

Thyroglossal duct cysts account for 70% of all congenital neck anomalies, and are the second most common benign neck mass, after lymphadenopathy.

Presentation is typically either as a painless rounded midline anterior neck swelling or, if infected, as a red warm painful lump. It may move with swallowing and classically elevates on tongue protrusion.

Thyroglossal duct cysts are epithelial lined cysts. They result from failure of normal developmental obliteration of the thyroglossal duct during development (8th-10th gestational week), and can thus occur anywhere along the course of the duct.

The epithelial lining of the cyst varies with location. Those that form near the tongue are lined by stratified squamous epithelium. The more common cysts located in the neck are lined by cells similar to thyroidal acinar epithelium.

Location

The cysts can occur anywhere along the course of the thyroglossal duct, although infrahyoid location is most common:

  • suprahyoid: 20-25% (less common in adults ~5%)
  • at the level of hyoid bone: ~30% (range 15-50%)
  • infrahyoid: ~45% (range 25-65%)

Typically, they are located in the midline (~70%) with those off-midline characteristically tucked next to the thyroid cartilage. Almost all thyroglossal duct cysts are located within 2 cm of the midline, with more inferior lesions tending to be off midline.

Associations
Ultrasound

Unless infected, they are painless, fluctuant masses which spread the strap muscles. The fluid is usually anechoic and the walls are thin, without internal vascularity.

However, in some cases, the internal fluid may contain debris.  This is particularly the case in an adult patient where cysts may be complex heterogeneous masses.

If there is associated infection, there may be surrounding inflammatory change.

CT

At CT, thyroglossal duct cysts are thin walled, smooth, well defined homogeneously attenuating lesions with an anterior midline or para-midline location. The generally accepted rule is that they should be within 2cm of the midline. The may demonstrate slight rim (capsular) enhancement.

The sternocleidomastoid muscle is typically displaced posteriorly or posterolaterally. In some cases, thyroglossal duct cysts may be embedded in the infrahyoid (strap) muscles.

MRI
  • T1: variable
    • low signal: if low protein or uncomplicated
    • high signal (most common 6) due to
      • previous haemorrhage or infection
      • high protein (probably due to previous complication)
  • T2: typically high signal
  • T1 C+ (Gd)
    • no enhancement in uncomplicated cysts
    • thin peripheral enhancement may be seen

Complete resection of the cyst and duct up to the foramen caecum is curative. The Sistrunk procedure includes resection of the middle third of the hyoid bone. There is small risk of recurrence (~2.5%).

Complications
  • infection
  • malignancies do occur but are rare

The differential is that of midline neck masses:

Ultrasound - general index
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Article information

rID: 2177
Section: Pathology
Synonyms or Alternate Spellings:
  • Thyroglossal duct cyst (TGDC)
  • TGDC
  • Thyroglossal duct cysts
  • Thyroglossal duct cysts (TGDC)'s

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Cases and figures

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