Inclusion Criteria:

          1. Age ≥ 18 and ≤ 70 at the time of signing informed consent

          2. Patient must have histologically confirmed newly diagnosed polymorphic or monomorphic
             PTLD defined according to the 2016 World Health Organization (WHO) classification
             criteria.

          3. Diagnostic archival tissue available for review and correlative studies

          4. Previous solid organ or allogeneic hematopoietic stem cell transplant

          5. Measurable disease

          6. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2

          7. Patients must have adequate organ and marrow function

          8. Negative urine or serum pregnancy test for women of childbearing potential

          9. Patients must be able to understand and to sign a written consent document.

        Exclusion Criteria:

          1. Previous treatment for PTLD with the exception of immunosuppression reduction

          2. Known involvement of the central nervous system by the PTLD

          3. Known allergic reactions against foreign proteins

          4. Uncontrolled inter-current illness including active infection, acute graft versus host
             disease and/or transplant organ rejection

          5. Active concurrent malignancy with the exception of non-melanoma skin cancer, carcinoma
             in situ of the cervix or localized prostate cancer

          6. Severe non-compensated diabetes mellitus

          7. Pre-existing neuropathy grade 2 or greater

          8. Pregnant or lactating

          9. Psychiatric illness / social situations that would limit compliance with study
             requirements

         10. Patients with previous hypersensitivity to Rituximab

         11. Known HIV positive.