A thyroglossal duct cyst (TGDC) is the most common congenital mass that forms in the neck. It is a fluid-filled sac, or cyst, typically found in the center of the neck, often presenting in children and adolescents. A TGDC is almost always benign. The cyst results from a developmental irregularity that occurs before birth.
How Thyroglossal Duct Cysts Form
The formation of a thyroglossal duct cyst begins with the early development of the thyroid gland. The thyroid gland starts at the base of the tongue and migrates downward to its final position in the lower neck. This migration creates a narrow channel called the thyroglossal duct.
This duct typically disappears completely by the tenth week of gestation. If parts of the duct fail to close off, a persistent tract remains. Cells within this remnant duct secrete fluid or mucus, leading to cyst formation.
The cyst can occur anywhere along the original path of the duct, but it is most frequently located in the midline of the neck, just below the hyoid bone. The hyoid bone is anatomically significant because the duct tract passes close to or through it, influencing the cyst’s location and surgical removal.
Recognizing the Signs
The most frequent sign of a thyroglossal duct cyst is a soft, smooth lump in the front and center of the neck. This mass is usually painless and causes no symptoms unless it becomes infected. The cyst size varies and may become noticeable after an upper respiratory infection causes swelling.
A distinguishing feature is the cyst’s characteristic movement. When a patient swallows or sticks out their tongue, the lump moves upward in the neck. This movement happens because the cyst is attached to the duct remnants, which connect to the base of the tongue and the hyoid bone.
The cyst can become infected, often prompting medical attention. An infected cyst rapidly swells and becomes tender, red, and warm. Severe infection may rupture and drain mucus or pus through a small opening in the skin, known as a fistula or sinus tract.
Confirming the Diagnosis and Treatment
Diagnosis
The process of confirming a TGDC begins with a physical examination, checking for the lump’s movement during swallowing and tongue protrusion. Imaging studies are then used to confirm the diagnosis and provide anatomical detail. An ultrasound is the first step, as it confirms the mass is fluid-filled and helps distinguish it from other neck masses.
Before surgical intervention, the physician must confirm that the patient has a normal, functional thyroid gland in its correct lower neck location. This is important because, in extremely rare cases, the cyst represents the only thyroid tissue the person has. If malignancy is a concern, a fine-needle aspiration (FNA) may be performed to collect cells for laboratory analysis.
Treatment
Surgical removal is the standard and most definitive treatment for a thyroglossal duct cyst to prevent chronic infection and recurrence. The preferred surgical procedure is called the Sistrunk procedure, which addresses the unique anatomy of the duct. This operation involves removing the cyst, the entire thyroglossal duct tract up to the tongue base, and the central portion of the hyoid bone.
Removing the segment of the hyoid bone greatly reduces the chance of the cyst returning. If only the cyst itself is removed, the recurrence rate can be as high as 50% or more, because the duct’s microscopic remnants are left behind. The Sistrunk procedure is associated with much lower recurrence rates.
Outlook and Recovery
Recovery
The prognosis following a successful Sistrunk procedure is excellent. The procedure is performed under general anesthesia, and most patients are observed in the hospital for one night. Recovery is relatively short, requiring about five to seven days before a child can return to normal activities.
Patients may experience temporary discomfort or a different feeling when swallowing due to the removal of the small segment of the hyoid bone. Pain is managed with medication, and the incision site is monitored for signs of infection. The recurrence rate of the cyst is low, typically between 3% and 10%.
Malignancy Risk
The risk of the cyst containing malignant cells is very low, occurring in approximately 1% of cases that undergo surgical removal. When malignancy does occur, it is most frequently papillary carcinoma, a highly treatable form of thyroid cancer. In these rare instances, the prognosis remains favorable, and the Sistrunk procedure is often the primary treatment.