Thymic ultrasound II. Diagnosis of aberrant cervical thymus

Background. The aberrant cervical thymus is an uncommon entity to be considered in the differential diagnosis of neck masses in children, so a preoperative diagnosis has rarely been made. Objective. The purpose of this study was to assess the ultrasound features of aberrant cervical thymus and determine if recognition of the previously described unique intrathymic echo pattern allows us to make a specific diagnosis. Materials and methods. We present four patients with an aberrant cervical thymus and one patient with a cervical thymic cyst. All five patients had ultrasound, which was evaluated with special attention to the detailed echo pattern of the mass. In two patients, the mass was surgically removed. Four patients had MRI, which was evaluated. Medical records were reviewed. Results. In all cases, the mass was painless and nontender. All occurred in the expected path of the thymopharyngeal duct. In four patients, ultrasound demonstrated multiple echogenic linear structures and foci previously described as characteristic echo pattern of normal thymic tissue. In one patient, ultrasound showed a large cystic mass and echogenic solid component superiorly with a characteristic echo pattern of normal thymus. Conclusions. The ultrasound appearance of thymic tissue is unique, allowing a specific diagnosis of aberrant cervical thymus, Biopsy or other imaging is probably not indicated when it presents with typical clinical features.