Thyroglossal Duct Cyst

Jay Paul Willging

History

A 3-year-old black boy was noted to have a swelling in the superior neck in the midline. It came up rapidly in association with a upper respiratory infection (URI). The mass was painful to palpation with no overlying erythema. Antibiotics caused the mass to decrease in size slightly, and the tenderness resolved.

The mass was located 1 cm below the hyoid bone in the midline of the neck. It was not fluctuant to palpation, but it did feel cystic and firm. It was not freely mobile.

Differential Diagnosis—Key Points

1. Thyroglossal duct cyst. The thyroid originates in the tongue base and descends inferiorly through the neck to assume its final position in the base of the neck. Remnants of the descending tissue may persist in the anterior compartment of the neck, lying near the midline. The remnant may lie anywhere from the hyoid to the clavicles. Lingual thyroglossal duct cysts may be encountered that manifest as a tongue base mass without any visible abnormality in the neck. Antibiotics have little effect beyond correction of an acute infection within the mass. The mass tends to persist despite antibiotic treatment.

2. Dermoid. Epithelial inclusion cysts (dermoids) are often associated with developmental fusion planes. The dermoid is a benign accumulation of squamous debris. They may become infected and present with pain and swelling, or they may present as a solitary mass. In the neck, they are most commonly found above the level of the hyoid bone, a location rarely found with thyroglossal duct cysts. Antibiotics have limited effect beyond correction of an acute infection. The mass tends to persist after antibiotic treatment.

3. Lymphadenopathy. Cervical adenopathy may occur in any of the nodal chains. They are often found laterally in the neck. Mid-line nodes are commonly found in the sub-mental area as well as in the base of the neck, as the paratracheal nodes. Antibiotics will often promote resolution of reactive adenopathy.

5. Neoplasm. Neoplasms may develop in the neck and must always be considered in the evaluation of a child with a neck mass. In the pediatric population, around 10% of masses will be neoplasms. The tissue type would be dependent on the organ from which it derived.

Test Interpretation

1. Computed tomography (CT) imaging. The location and physical characteristic of an anterior compartment mass often suggest the diagnosis of a thyroglossal duct cyst. When this is suspected, no imaging of the mass is necessary. When there is doubt, a CT provides good visualization of the lesion and its anatomic relationships to other structures. It will show a low-density mass, but rarely the associated thyroglossal duct, which traverses the hyoid bone, to terminate in the tongue base.

If a CT is obtained, it is important to evaluate the films to confirm the thyroid gland lies in its proper location at the base of the neck. It is possible that the only functioning thyroid tissue resides within the mass.

2. Magnetic resonance imaging (MRI). MRI will provide similar visualization of the mass and surrounding structures as a CT, but it is not the preferred test because of its higher costs and longer acquisition times. Because most patients with thyroglossal duct cysts are young, sedation is often required for MRI. Many fewer children require sedation for a CT scan.

3.