The authors describe a case of primary cerebral T-cell lymphoma observed in a 68-year-old man. The patient suffered from disseminated follicular carcinoma of the thyroid and the clinical picture has been dominated by neurological symptoms of presumed metastatic origin. Primary cerebral lymphoma was discovered at autopsy. Histologically, it proved to be a high-grade malignant pleomorphic non Hodgkin's lymphoma whose T-cell lineage was confirmed by immunohistochemistry. The patient did not manifest any congenital or acquired immune deficiency. There were neither cerebral metastases of the thyroid cancer nor any evidence for extracranial involvement by a lymphoma. Providing a brief literature review of cerebral T-cell lymphomas, the authors discuss some major traits of this exceptional form of lymphoid neoplasia of the central nervous system. Differential diagnostic and theoretical implications raised by cerebral lymphomas as second malignant tumors synchronously or metachronously associated with other malignant diseases are envisaged.