Primary cerebral lymphoma and membranous nephropathy: a still unreported association.

Paraneoplastic nephrotic syndrome (NS) in the setting of membranous nephropathy (MN) is a well-known and often prodromal complication of renal and extrarenal malignancy. Primary cerebral lymphoma is a rare neoplasm uncommonly investigated in the setting of NS. We describe for the first time a case of primary cerebral lymphoma in association with MN. An elderly woman presented for renal biopsy because an NS had been diagnosed previously and treated by steroid therapy. Primary membranous glomerulonephritis was diagnosed and immunosuppressive therapy was started. Twenty days later, she was readmitted because of left hemiplegia. Computed tomography and subsequent nuclear magnetic resonance evaluation of the brain documented an extensive cerebral space-occupying lesion. A cerebral malignant lymphoma was diagnosed at intraoperative histologic evaluation, and subsequent light microscopic and immunohistochemical studies allowed the diagnosis of peripheral T-cell lymphoma. Extensive clinical workup, including bone marrow biopsy, documented the lack of any neoplastic involvement outside the brain. Primary cerebral non-Hodgkin's lymphoma of peripheral T-cell derivation consequently was diagnosed. This case suggests that patients with MN, particularly elderly patients, should undergo complete screening for neoplasms. The absence of specific guidelines on this topic may be due partly to the lack of extensive description of all newly identified cases. All cases should be reported to evaluate whether this association is causal or fortuitous.