can be seen as a flattened strawberry-like lump at the base of the tongue. Complications Infection An infected thyroglossal duct cyst can occur when it is left untreated for a certain amount of time or simply when a thyroglossal duct cyst hasn't been suspected. The degree of infection can be examined as major rim enhancement has occurred, located inferior to the hyoid bone. Soft tissue swelling occurs, along with airway obstruction and trouble swallowing, due to the rapid enlargement of the cyst. With infections, there can be rare cases where an expression of fluid is projected into the pharynx causing other problems within the neck. Thyroglossal Fistula A thyroglossal duct cyst may rupture unexpectedly, resulting in a draining sinus known as a thyroglossal fistula. Thyroglossal fistula can develop when the removal of the cyst has not been fully completed. This is usually noticed when bleeding in the neck occurs, causing swelling and fluid ejection around the original wound of removal. Thyroglossal duct cyst carcinoma Rarely (in less than 1% of cases), cancer may be present in a thyroglossal duct cyst. These tumors are generally papillary thyroid carcinomas, arising from the ectopic thyroid tissue within the cyst. Causes Thyroglossal Duct Cysts are a birth defect. During embryonic development, the thyroid gland is being formed, beginning at the base of the tongue and moving towards the neck canal, known as the thyroglossal duct. Once the thyroid reaches its final position in the neck, the duct normally disappears. In some individuals, portions of the duct remain behind, leaving small pockets, known as cysts. During a person's life, these cyst pockets can fill with fluids and mucus, enlarging when infected, presenting the thyroglossal cyst. Embryology The thyroglossal tract arises from the foramen cecum at the junction of the anterior two-thirds and posterior one-third of the tongue. Any part of the tract can persist, causing a sinus, fistula or cyst. Most fistulae are acquired following rupture or incision of the infected thyroglossal cyst. A thyroglossal cyst is lined by pseudostratified, ciliated columnar epithelium while a thyroglossal fistula is lined by columnar epithelium. Diagnosis Diagnosis of a thyroglossal duct cyst requires a medical professional, and is usually done by a physical examination. It is important to identify whether or not the thyroglossal cyst contains any thyroid tissue, as it can define the degree of cyst that is being dealt with. Diagnostic procedures for a thyroglossal cyst