A persistent thyroglossal duct is a usually benign medical condition in which the thyroglossal duct

Thyroglossal duct

The thyroglossal duct is an embryological anatomical structure forming an open connection between the initial area of development of the thyroid gland and its final position....

, a structure usually only found during embryonic development

Embryology

Embryology is a science which is about the development of an embryo from the fertilization of the ovum to the fetus stage...

, fails to atrophy. The duct persists as a midline structure forming an open connection between the back of the tongue and the thyroid gland.

Background

Early during embryonic development

Embryology

Embryology is a science which is about the development of an embryo from the fertilization of the ovum to the fetus stage...

, the thyroglossal duct

Thyroglossal duct

The thyroglossal duct is an embryological anatomical structure forming an open connection between the initial area of development of the thyroid gland and its final position....

 is a midline structure that connects the back of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 to the thyroid gland. The duct usually disappears, or atrophies, during the ninth week of gestation so that in most individuals the thyroid does not connect to the tongue. In individuals with a persistent thyroglossal duct, the duct fails to atrophy, and the connection between the thyroid gland and the tongue is maintained.

Complications

A persistent thyroglossal duct may become fluid filled, forming a thyroglossal duct cyst, the most common type of congenital neck malformation. Such cysts account for approximately 2-4% of all neck masses.

Very rarely, the persistent duct can become cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

ous, called thyroglossal duct carcinoma. In the case of thyroglossal duct carcinoma, the cancerous cells are ectopic thyroid tissue that has been deposited along the thyroglossal duct and usually follows exposure to radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

.