Everolimus Plus Rituximab for Relapsed/Refractory Diffuse Large B Cell Lymphoma

Participants will receive oral Everolimus and intravenous rituximab for DLBCL that has relapsed or been refractory to prior therapy. * Each treatment cycle lasts 28 days (4 weeks). Everolimus will be taken orally, once daily in the morning. * Rituximab will be administered by an intravenous (IV) infusion on Days 1, 8, 15 and 22 of Cycle 1. In Cycles 2-6, rituximab will be administered only on Day 1 of each cycle. * Participants will come into the clinic weekly during the first cycle, then on Day 1 of all cycles thereafter. The following tests and procedures will be performed: * Weekly During Cycle 1: blood tests * Day 1 of all Subsequent Cycles: brief physical examination; review of current medications, treatments, symptoms and side effects; vital signs; performance status evaluation; blood tests. * A full body CT and PET scan to assess the participants tumor will be done within 7 days of completing cycles 2, 4, 6, 9 and 12. Responding subjects may receive up to 6 cycles of Everolimus plus rituximab, and an additional 6 months of oral Everolimus for participants continuing to respond.