Primary central nervous system lymphoma with paraproteinemia.

BACKGROUND: Although 34% to 54% of cases of extraneural non-Hodgkin's lymphoma (NHL) of the B-cell type are associated with monoclonal paraproteinemia, primary central nervous system NHL (PCNSL) with paraproteinemia has rarely been reported. The authors present herein a case of PCNSL with monoclonal immunoglobulin M (IgM) paraproteinemia. METHODS AND RESULTS: A 78-year-old woman was referred to our hospital because of hemiparesis and epilepsy. Magnetic resonance imaging showed a round mass in the left frontal region. Serum IgM was 3,820 mg/dL, and immunofixation revealed an IgM kappa monoclonal paraprotein. No lymphoplasmacytic infiltration was observed on bone marrow aspiration. The brain tumor was totally resected. The pathological diagnosis was NHL (diffuse, large B cell). The results of immunohistochemical staining for IgM were strongly positive in the tumor cells. CONCLUSION: This type of PCNSL has rarely been reported and little is known about it. It is possible that the true incidence of paraproteinemia caused by PCNSL is higher than has been thought. The clinical features of the tumor and pertinent literature are reviewed.