Cervical thymic cysts in children.

Thymic cysts are a rare cause of cervical masses in children. The cysts usually appear between ages 6 and 7 years and present as a soft swelling in the anterior triangle of the neck. The cysts may be small and unilocular or large and multilocular; they produce few symptoms. The etiology is unclear but may be related to remnants of tissue left in the cervical region when the thymus gland descends from the neck to the mediastinum during embryologic development. Forty-three cases of cervical thymic cysts have been reported in patients under 20 years of age. Two additional cases are reported in boys 5 and 9 years of age.