Abnormal Locations of Thymic Tissue as an Uncommon Cause of Neck Masses in Children: A Practical Approach

Background: The thymus gland is a lymphoid organ normally located in the anterior mediastinum. Location abnormalities of the thymus, such as ectopic thymus or the superior herniation of a mediastinal thymus, could be responsible for the occurrence of cervical masses in pediatric patients, raising concerns among clinicians. The knowledge of these conditions is essential for a thorough differential diagnosis and for preventing unnecessary invasive procedures. Methods: Descriptive retrospective series of three patients with a cervical mass, that was later diagnosed as ectopic thymic tissue. Results: The thymus has a unique and distinctive ultrasound appearance that is the keystone to detecting thymic parenchyma in locations other than anterior mediastinum. In selected patients, an accurate ultrasound could be conclusive for the diagnosis, with no need for further and potentially risky procedures. Conclusions: This case series supports the use of ultrasound in both diagnosis and follow-up of thymus location abnormalities, advocating a minimal invasive and conservative approach.