Thyroglossal Duct Remnant

Epidemiology

Thyroglossal duct remnants are congenital lesions that arise from anomalous development and migration of the thyroid gland. These remnants may accumulate fluid and be referred to as thyroglossal duct cysts. Thyroglossal duct cysts are the most common midline neck mass in children. The majority of cases present in children < 10 years of age. These lesions may be seen in young adults. Less than 2% of cases arise in patients > 60 years of age. No gender predilection has been reported.

Clinical Findings

Thyroglossal duct cysts usually present as nontender, gradually increasing, midline neck masses. The average size at presentation is 2 to 4 cm. Recent enlargement may occur as a result of an associated upper respiratory tract infection. Because thyroglossal duct cysts are often attached to the tongue or hyoid bone, these lesions characteristically move when the tongue is protruded.

Embryology

The thyroid gland is the first endocrine gland to appear in the developing fetus and begins its embryogenesis around day 24 of gestation. The gland arises from an endodermal thickening in the midline of the developing tongue base. This area is known as the foramen cecum and is located posterior to the apex of the circumvallate papilla. The thyroid gland descends as a result of elongation of the embryo and growth of the tongue. The developing gland migrates as a bilobed diverticulum and forms an epithelial lined cord during descent. Normal involution of the thyroglossal duct occurs between the eighth and tenth weeks of gestation. Failure of involution of the epithelial cord results in thyroid remnants and may result in the formation of a thyroglossal duct cyst. Cyst formation is believed to occur from inflammatory changes that stimulate secretion of fluids within the ductal remnants or to trapping of fluids produced from residual secretory epithelium located in the epithelial cord remnant.