Because rituximab and CHOP have only limited activity in the CNS, it is unlikely that either of the treatment regimens will prevent the CNS relapses.20 Even when initial CNS prophylaxis with intrathecal MTX is provided, CNS relapses can occur as illustrated by 2 patients with lymphoma of the testes in our study.21 Recently, the CNS‐IPI as risk model for CNS relapse in patients with DLBCL was established to identify patients at highest risk for CNS relapse.14 In patients with a low‐risk CNS‐IPI, less than 1% showed a CNS relapse. This evidence concerns the gene DDIT3 and lymphoma.