A thyroglossal duct cyst (TGDC) is a neck lump that develops from remnants of a structure present before birth. While congenital, these cysts often become noticeable later in life, even into adulthood. They are the most common congenital anomaly of the neck, though relatively rare.
The Thyroglossal Duct’s Origin
A thyroglossal duct cyst forms during thyroid gland development in the embryo. Around the third week of gestation, the thyroid gland begins as a small outgrowth from the base of the primitive pharynx, at the foramen cecum. From this point, the thyroid gland descends, migrating down the neck to its final position.
This migratory path creates a temporary tube-like structure known as the thyroglossal duct. Normally, this duct disappears by approximately the tenth week of gestation. However, in some individuals, portions of this duct fail to close off, leaving behind epithelial tissue remnants. These persistent remnants are the anatomical cause of a thyroglossal duct cyst, forming a potential space that can later accumulate fluid.
Factors Leading to Cyst Formation in Adults
Though congenital, thyroglossal duct remnants do not always result in an immediately apparent cyst at birth. The duct can remain dormant for years before becoming noticeable in adulthood. This delayed manifestation is often triggered by factors that lead to the accumulation of fluid or mucus within the remnant, causing it to swell.
A common trigger is infection, particularly upper respiratory tract infections, which can cause inflammation and expansion of the cyst. The epithelial lining within the persistent duct can also secrete mucus, which accumulates over time, leading to gradual enlargement. Trauma or irritation to the neck area might also contribute to the cyst’s sudden appearance or growth by inciting an inflammatory response.
Recognizing the Signs
A thyroglossal duct cyst in adults typically presents as a painless, soft, and movable lump located in the front of the neck, often near the midline. A distinctive characteristic is its tendency to move upward when an individual swallows or sticks out their tongue, due to its connection to the base of the tongue and the hyoid bone. The size of these cysts can vary, commonly ranging from 2 to 4 centimeters in diameter.
If the cyst becomes infected, symptoms include redness, tenderness, and swelling in the affected area. An infected cyst might rupture, leading to drainage through a small opening in the skin. Larger cysts can sometimes cause difficulty swallowing or, rarely, breathing issues.
How Thyroglossal Duct Cysts Are Diagnosed and Managed
Diagnosing a thyroglossal duct cyst typically begins with a physical examination, where a healthcare provider assesses the lump’s location, consistency, and movement with swallowing or tongue protrusion. Imaging studies then confirm the diagnosis and distinguish it from other neck masses. Ultrasound is often the preferred initial imaging modality. Computed tomography (CT) scans or magnetic resonance imaging (MRI) may also provide more detailed anatomical information. It is important to ensure that normally functioning thyroid tissue is present in its usual location, as the cyst can sometimes contain thyroid cells.
The standard management for a thyroglossal duct cyst is surgical removal, specifically a procedure known as the Sistrunk procedure. This operation involves excising the cyst, the entire thyroglossal duct tract, and the central portion of the hyoid bone, which the duct often wraps around or passes through. This comprehensive approach helps to minimize recurrence, with reported rates of approximately 0.6% to 5.5%. If the cyst is infected, antibiotics are typically administered to resolve the infection before surgical intervention.