Ectopic Thymic Tissue Presenting as a Neck Mass in Children: A Report of 3 Cases

Abstract

The presentation of ectopic cervical thymic tissue as an anterior neck mass is rare. We report 3 similar cases in 3 boys-2 whohada thymiccystand 1 whohadan ectopic cervical thymus. We discusstheradiographicpresentation on ultrasound and magnetic resonance imaging in these cases. Wealso review thetypical histologicpicture; histology is theonlywayof diagnosing thiscondition.

Clinical management of cervical ectopic thymus in children

“…During the seventh week, the bud-like thymic primordia elongate and become cylindrical, forming thymopharyngeal ducts that migrate caudally and medially to their final destination in the anterior mediastinum. Therefore, CET can be found along the line of descent from the mandibular area down to the mediastinum [1,2]. Cervical ectopic thymus usually presents as a solid or cystic cervical mass.…”

Accessory cervical thymus presenting in conjunction with a thyroglossal duct cyst

“…accessory thymus, as presented in the case above, is only found in 10-30% of all cervical thymic tissue cases [5,6]. Approximately 50% of all cervical thymic masses are continuous with the mediastinal thymus via direct extension or a solid cord of tissue [2].…”

“…The majority of cases of accessory cervical thymic tissue have been reported in patients younger than 20 years of age. In 90% of the cases the patients were asymptomatic [6]. In addition, accessory thymic tissue most often presents on the left side of the neck (63%), is diagnosed between the ages of 3 and 8 years (64%), and is most common in males (73%) [7].…”

“…The path of descent consists of passing from the piriform sinus through the thyrohyoid membrane and exiting between the carotid artery and vagus nerve. The gland remains lateral to the thyroid capsule as it reaches its final position anterior to the great vessels in the mediastinum [6]. The path of descent correlates with why most ectopic thymic lesions are found at the level of the thyroid gland anterior to the carotid artery and deep to the anterior border of the sternocleidomastoid muscle [8].…”

Thymus

“…Surgical removal and histological examination is often the only way to prove the diagnosis (Cigliano et al 2009;Felgentreff et al 2009;Meyer et al 2010;Nasseri and Eftekhari 2010). The cystic version of aberrant thymic tissue is more abundant than the "classical" solid form.…”