A 25-year-old man presented with an anterior midline cystic swelling in the neck. When he protruded his tongue the cyst elevated.

Thyroglossal tract cysts develop at any point from the foramen caecum to the thyroid along the line of the vestigal thyroglossal duct. Most occur below the level of the hyoid bone and in people under 30 years.

Thyroglossal tract cysts are abnormal fluid-filled sacs that develop along the path of a structure called the thyroglossal duct. To understand this, let’s break it down step by step.

1. Thyroglossal tract: During the early stages of fetal development, the thyroid gland (a butterfly-shaped gland located in the neck) forms at the base of the tongue in an area called the foramen caecum. As the fetus grows, the thyroid gland descends down the neck to its final position in front of the trachea (windpipe). The path it takes while descending is called the thyroglossal tract.
2. Vestigial thyroglossal duct: The thyroglossal tract is initially a duct-like structure that connects the thyroid gland to the base of the tongue. However, as the thyroid gland descends, the duct usually disappears, leaving only a remnant called the vestigial thyroglossal duct.
3. Development of cysts: In some cases, the vestigial thyroglossal duct may not completely disappear, and remnants of it can persist. These remnants can potentially develop into cysts. Thyroglossal tract cysts usually form anywhere along the path of the vestigial thyroglossal duct, from the foramen caecum (at the base of the tongue) to the final location of the thyroid gland in front of the trachea.
4. Location and age group: Most thyroglossal tract cysts occur below the level of the hyoid bone, which is a small U-shaped bone in the neck. They are commonly found in people who are under 30 years old. However, it’s important to note that thyroglossal tract cysts can occur at any age, including in adults.

In summary, thyroglossal tract cysts are fluid-filled sacs that develop along the vestigial thyroglossal duct, a remnant of the developmental path of the thyroid gland. They can occur anywhere from the base of the tongue to the final location of the thyroid gland. Most of these cysts are found below the level of the hyoid bone and are typically observed in individuals under 30 years of age.