Pembrolizumab in Relapsed or Refractory Extranodal NK/T- Cell Lymphoma, Nasal Type and EBV-associated Diffuse Large B Cell Lymphomas

Inclusion Criteria: * Be willing and able to provide written informed consent/assent for the trial. * Be ≥ 18 years of age on day of signing informed consent. * Have measurable disease based on defined as at least one lesion that can be accurately measured in at least two dimensions with a spiral CT scan, PET/CT scan, or MRI. Minimum measurement of \>1.5 cm in longest diameter by \> 1.0 cm in short axis. * Have a performance status of 0 or 1 on the ECOG Performance Scale. * Demonstrate adequate organ function, all screening labs should be performed within 10 business days of treatment initiation with the exception of beta-HCG (72 hours), if applicable. * Female subject of childbearing potential should have a negative serum pregnancy within 72 hours prior to receiving the first dose of study medication. * Male subjects of childbearing potential (Section 5.7.1) must agree to use an adequate method of contraception as outlined in Section 5.7.1- Contraception, starting with the first dose of study therapy through 120 days after the last dose of study therapy. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the subject. Exclusion Criteria: * Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy within 4 weeks of first dose of treatment or used an investigational device within 4 weeks of the first dose of treatment. * Has a diagnosis of immunodefi…