Thyroglossal Duct Cyst (TDC)

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Diagnosis Definition

Thyroglossal duct cyst (TDC) is the most common congenital cystic lesion and pediatric mass in the neck
It occurs along the midline, between the base of the tongue (foramen cecum) and the thyroid bed
TDCs present as a palpable neck mass; they can acutely enlarge and become painful when secondarily infected
40% of TDCs are associated with an ectopic thyroid gland

Imaging Findings

On CT and MRI, a TDC will be seen as a midline cystic lesion between the base of the tongue and the thyroid bed, usually at or below the level of the hyoid bone
MRI provides a high degree of diagnostic accuracy for TDCs, but is rarely required for the diagnosis
Although TDCs are invariably hyperintense on T2-weighted MR images, T1-weighted signal intensity is variable
Peripheral rim enhancement is sometimes observed on post-contrast MR images and is suggestive of previous infection

Pearls

To prevent recurrence, excision of a TDC involves resection of the entire track, including the midline hyoid (Sistrunk procedure)
TDCs can be a source of papillary thyroid carcinoma; calcification and a new enhancing soft tissue component are suggestive of carcinoma
Differential considerations include a dermoid, which may contain fat-dense or fat-saturating tissue, and a cystic lymph node

References

Ahuja AT, Wong KT, King AD, Yuen EH. Imaging for thyroglossal duct cyst: the bare essentials. Clinical Radiology 2005; 60(2):141-8
Oomen KP, Modi VK, Maddalozzo J. Thyroglossal duct cyst and ectopic thyroid: surgical management. Otolaryngologic Clinics of North America 2015; 48(1):15-27

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