Malignant lymphomas of the nervous system.
In a series of some 7,000 patients with tumors of the central nervous system, 208 patients (about 3%) had some form of a malignant lymphoma. Slightly less than half of these tumors were primary in the brain; the remainder had cranial involvement as part of a generalized process. The tumors consisted of Hodgkin's disease, lymphosarcomas, reticulosarcomas and plasmacytomas. The brain was involved in one of two ways: either as localized tumor masses resembling certain gliomas, or as diffusely invasive neoplasms resembling exudative cellular inflammatory processes. They had a peculiar predilection for the septum pellucidum but occurred also in the cerebral lobes, basal ganglia, brain stem and cerebellum. They all produced a fibrillary stroma of reticulin fibers and they spread along the perivascular spaces, in the cerebrospinal subarachnoid space, or intraventricularly on and beneath the ependymal lining. One type of lymphoma often fused into another - thus a single tumor often consisted of Hodgkin's sarcoma, lymphosarcoma and reticulosarcoma. In an addition series of 57 cases of spinal cord involvement by malignant lymphomas, there were no instances of a primary tumor; all patients had either primary lymphomas of the brain with secondary spread to the spinal subarchnoid space, or had spinal cord compression as a result of tumor in the vertebrae, the spinal epidural space, or the spinal dura. Hence the spinal cord involvement was a secondary manifestation of a lymphoma elsewhere. Peripheral nerve involvement by lymphomas resulted in destruction of myelin sheaths and axons by tumor cell infiltration and the neuropathy was always part of a generalized lymphomatosis.