Thyroglossal Duct Cyst (TDC)

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

KEY IMAGES

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

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