This is a prospective, multicenter phase II trial designed to evaluate the safety and activity of the combination of Bendamustine, Lenalidomide and Rituximab (R2-B) in patients with first relapsed/refractory mantle cell lymphoma (MCL) and the efficacy and safety of a maintenance treatment with Lenalidomide for 18 months from the end of R2-B (from month 7 to 24) for those responding to the induction.