 This study will test the standard R-CHOP21 against R-CHOP21 plus lenalidomide. The purpose is to see whether adding lenalidomide works better and is as safe as R-CHOP by itself. This study is only for patients with ABC type DLBCL who have not yet been treated. Lenalidomide is not approved for use in DLBCL. Its use in this disease is experimental. In this study, the experimental treatment is lenalidomide R-CHOP21 x 6. 