Patients with increased level of serum IL-10 had shorter time to CNS invasion, and might predict the risk of SCNSL in patients with DLBCL. And when 0.2 < CSF IL-10/plasmaIL-10 ratio < 5.0, this ratio also could be a reliable biomarker to diagnose SCNSL. The gene discussed is IL10; the disease is diffuse large B-cell lymphoma.