Tafasitamab (MOR00208) is currently in development for the treatment of R/R DLBCL. An ongoing, single-arm, phase II, open label, multicenter study (MOR208C203) is evaluating the efficacy and safety of tafasitamab combined with lenalidomide in patients with R/R DLBCL. In order to establish a lenalidomide monotherapy as a control cohort, this observational study aims to collect retrospective lenalidomide monotherapy data from real-world-evidence and to compare it with the tafasitamab-lenalidomide combination therapy.