Ectopic cervical thymus: an uncommon diagnosis in the evaluation of pediatric neck masses

Ectopic cervical thymic tissue is an uncommon cause of neck masses in children, with fewer than 100 cases reported in children who presented with primary neck masses. To illustrate the unique characteristics of these tumors, we report the case of a 13-month-old boy with ectopic thymic tissue presenting with asymptomatic, bilateral, and solid cervical masses. This case report highlights several unique findings: (1) the rare nature of solid thymic tumors compared with cystic lesions, (2) the utility of magnetic resonance imaging scanning with and without fat suppression for diagnosis, and (3) the risks of surgical removal of thymic tissue in children. Despite its infrequent occurrence and often asymptomatic presentation, ectopic cervical thymus masses should be included as a rare cause of cervical masses in the pediatric population. Awareness of this diagnosis will allow for appropriate preoperative diagnostic studies, which may preclude the need for biopsy.