Diagnosis: Thyroglossal duct cysts
• The thyroglossal duct originates in the foramen caecum of the posterior oral cavity, and extends along the midline to the ultimate position of the thyroid.
• Thyroid-type neoplasms may arise in thyroglossal duct cysts, or in ectopic thyroid tissue, which frequently exists adjacent to thyroglossal duct cysts.
• Papillary carcinoma is the most common thyroid-type neoplasm in this context.
• Medullary carcinoma arises from “C” cells (or their precursors), which migrate into the thyroid from the fourth/fifth branchial pouch.
• The thyroglossal duct does not contain “C” cells, and medullary carcinoma would, therefore, be highly unusual in thyroglossal duct remnants.
