Case 7

Discussion:

Thyroglossal duct cyst (TGD) is the most common congenital neck mass, accounting for 70 percent of congenital neck anomalies. About half present before 20 years of age, with a second group of patients presenting in young adulthood. Located in the midline (75 percent) or slightly off-midline (25 percent). About 80 percent are located either at or below the level of the hyoid bone. Usually manifests as an enlarging, painless mass in a pediatric or young adult patient. Some present with recurrent infections. About 1 percent are associated with thyroid carcinoma arising from ectopic. About 80 percent are of the papillary type.   Nodal spread is much less common than in primary carcinomas arising in the thyroid gland. The recurrence rate following this procedure is 2.6 percent.

On all radiologic images, a thyroglossal duct cyst manifests as a cystlike mass either in the midline of the anterior neck at the level of the hyoid bone or within the strap muscles just off the midline.

On CT scans, they usually appear as a smooth, well-circumscribed mass anywhere along the vertical course of the vestigial thyroglossal duct in the midline of the anterior neck at the level of the hyoid bone or within the strap muscles just off the midline. The mass has a thin wall and homogeneous attenuation, the values of which correspond to those of fluid (10–18 HU). Elevated attenuation values of the fluid cyst reflect its increased protein content and generally correlate with a history of prior infections. Although most are usually unilocular, septations may be seen occasionally. Peripheral rim enhancement is usually observed on contrast-enhanced scans.