Monomorphic PTLD comprise more than 70% of PTLDs and diffuse large B-cell lymphoma is the predominant subtype. However, none of the trials have been performed for the specific population of DLBCL type monomorphic PTLD. The investigators will select Patients with proven, measurable monomorphic PTLD of DLBCL after solid organ transplantation (e.g. heart, lung, liver or kidney etc.). Patients having PTLD with or without Epstein-Barr virus (EBV) association, positive for CD20 monomorphic DLBCL type. The B-R treatment will continue up to 6 cycles with interval of 21 days. Patients will receive 375 mg/m2 on day 1 and bendamustine 120 mg/m2 by intravenous infusion on day 2 and 3 in the first cycle. From the 2nd to 6th cycle, rituximab will be administered subcutaneously at a fixed dose of 1400 mg and bendamustine 120 mg/m2 by intravenous infusion on day 1 following administration of rituximab and day 2. On the first day of infusion of bendamustine in each cycle, palonosetron 0.25 mg will be given as a single intravenous injection about 30 minutes before infusion of bendamustine. Pegfilgrastim 6 mg will be administered as a single subcutaneous injection between 24 to 48 hours after completion of chemotherapy at each cycle. Based on relatively good safety profile and efficacy of bendamustine and rituximab (BR regimen), the investigators will investigate a feasibility of BR regimen in this immunocompromised patients with DLBCL type monomorphic PTLD.