congenital lesions

Eight-Year-Old Girl With Mass in Midline of Neck

By ALEXANDER K. C. LEUNG, MD--Series Editor, and WM. LANE M. ROBSON, MD
Dr Leung is clinical associate professor of pediatrics at the University of Calgary, and pediatric consultant at the Alberta Children’s Hospital. Dr Robson is medical director of the Childrens’ Clinic in Calgary, Alberta.

Volume 6 - Issue 1 - January 2007

WHATS YOUR DIAGNOSIS?


HISTORY

Eight-year-old girl with mass in midline of neck. Mass first noted about 6 months earlier. Patient is otherwise well; past health unremarkable. No symptoms of hypothyroidism.

PHYSICAL EXAMINATION

Patient not in distress. Respiratory rate, 18 breaths/min; heart rate, 76 beats/min; temperature, 37.2°C (98.8°F). Cystic mass, 0.5 cm in diameter; not tender; moves upward with protrusion of the tongue. Examination otherwise normal.

WHATS YOUR DIAGNOSIS?

(Answer on next page.)


ANSWER: THYROGLOSSAL DUCT CYST

Thyroglossal duct cysts are the most common cause of a midline neck mass in children.1 The cyst is a persistent remnant ofthyroglossal duct epithelial tissue.2

EMBRYOLOGY

The thyroid anlage arises from the foregut diverticulum at the site of the future foramen cecum at about the third week of gestation.3,4 As the neck develops, the thyroid gland descends along the midline of the neck, between the first and second branchial arteries, andventral to the hyoid bone and the developing laryngeal cartilage.1,4 The thyroid gland remains connected to the foramen cecum by the thyroglossal duct during the descent. A cyst results when the thyroglossal duct fails to involute after the descent of the thyroid gland.

EPIDEMIOLOGY

The exact incidence is not known. Thyroglossal duct cysts account for approximately 70% of all congenital abnormalities of the neck.3 The sex ratio is equal.3,5 Most cases are sporadic. The cysts are occasionally inherited as an autosomal dominant disorder or,rarely, as an autosomal recessive disorder.6

CLINICAL MANIFESTATIONS

A thyroglossal duct cyst presents as a midline neck mass, which may move with swallowing and might move upward with protrusion of the tongue. However, its movement may be limited with protrusion of the tongue because of its persistent attachment to the foramen cecum.7

Approximately 1% of the cysts are located laterally, often on the left side.8 A thyroglossal duct cyst can occur at any site along the normal pathway of descent from the foramen cecum to the lower neck region.2 The most common site (61% of cases) is between the thyroid gland and the hyoid bone.8 Other potential sites include suprahyoidal (24%), suprasternal (13%), or intralingual (2%) locations.8

Although thyroglossal duct cysts are congenital, these lesions rarely present in the neonatal period.9 More commonly, the cysts are noted in preschool children,9 sometimes after an upper respiratory tract infection. At least 50% of the lesions are diagnosed in the second decade of life.7 Some do not present until adulthood. Presentation in the elderly is rare.10

COMPLICATIONS

Thyroglossal duct cysts commonly present as an infected neck mass (Figure).11 Recurrent infections are common if the lesion is not excised. Rarely, a thyroglossal duct cyst might cause extrinsic airway compression or intralaryngeal extension with resultant dyspnea or hoarseness.8 An intralingual thyroglossal duct cyst might result in dysphagia or speech impairment.8

A thyroglossal duct cyst has the potential for malignant transformation during childhood, but this is uncommon.1,10 Approximately 75% to 85% of thyroglossal duct malignancies are papillary adenocarcinomas. Follicular cell and squamous cell carcinomas also occur.1,10

DIFFERENTIAL DIAGNOSIS

The differential diagnosis includes midline dermoid cyst, ectopic thyroid tissue, lymphadenopathy, cystic hygroma, branchial cleft cyst, lipoma, lymphangioma, hemangioma, and sebaceous cyst.

HISTOPATHOLOGY

Thyroglossal duct cysts are lined by pseudostratified ciliated columnar epithelium (61% of cases), stratified squamous epithelium (38%), transitional epithelium (7%) or cuboidal epithelium (7%).8 The cysts contain colloid material with cholesterol crystals and phagocytes.1

DIAGNOSTIC STUDIES

Ultrasonography can be used to confirm the cystic nature of the lesion and the presence of a normal-appearing and normally situated thyroid gland. The ultrasonographic appearance of the lesion can be anechoic, homogeneously hypoechoic, or heterogeneous.1,12

TREATMENT

TheSistrunk procedure is the surgical treatment of choice.4,12 The procedure includes excision of the cyst, the thyroglossal tract, and the central portion of the hyoid bone to prevent recurrence.4,12