MRI of cervical masses of thymic origin.

Abstract

Thymic diseases can arise from remnants of thymic tissues along the path of fetal descent and may simulate thyroid tumors or lymphadenopathy. We present two patients with a cervical mass arising from the cervical thymus that was caused by incomplete descent of the thymus into the mediastinum. In one patient a cervical mass was surgically confirmed to be a cervical thymoma, which simulated a thyroid cancer on CT and 201Tl-scintigraphy. In another patient, cervical thymic hyperplasia arising from an incompletely descended thymus was surgically confirmed. The isointensity between the cervical mass and an enlarged mediastinal thymus was recognized on MRI. If a cervical mass is located in the region of the lower pole of the thyroid or if there is a connection or the same intensity between the cervical mass and the mediastinal thymus on MRI, a diagnosis of a cervical mass of thymic origin should be considered.