Malignant, predominantly lymphocytic thymoma with central and peripheral nervous system metastases.

Histologic features of an invasive mediastinal tumor found in a 25-year-old woman fulfilled the accepted criteria for diagnosis of predominantly lymphocytic thymoma. Histochemical and cell marker studies indicated that the neoplasm contained a preponderance of T lymphocytes. After surgical debulking of the mass, aggressive radiotherapy and chemotherapy eradicated all evidence of thoracic disease. However, six months after the initial diagnosis, rapid development of cranial nerve and brainstem metastases--without detectable recurrent disease elsewhere--resulted in the patient's death. Autopsy examination revealed the presence of peripheral nerve metastases as well. A review of the literature disclosed fewer than 10 cases of central nervous system metastasis from thymoma. In only two of these were there clinicopathologic features similar to those seen in this case.