Cervical thymoma and incidence of cervical thymus.

A case of cervical thymoma in a 51-year-old female is reported. The tumor was located on the left side of the anterior neck just beneath the left lower lobe of the thyroid gland and there was no connection to the mediastinal thymus gland. It was well encapsulated and lobulated on the cut-surface. Histologically, the tumor showed a mixed proliferation of lymphocytes and epithelial cells. Mitoses were frequently seen. Several tiny fragments of ectopic thymic tissue were found around the tumor. Cervical thymic tissue, considered to be the original site of the cervical thymoma, was studied and found macroscopically in 12 out of 657 patients with Basedow's disease (1.8%).