PDCD1 and lymphoma: The following keywords have been entered to rule the research: “Hodgkin lymphoma” OR “Non-Hodgkin lymphoma” OR “lymphoma” AND “Immunotherapy” AND “Immune checkpoint inhibitors” AND “anti-CTLA-4”, “anti-PD1”, anti-PDL1” AND “CAR-T cell therapy” AND “18F-FDG” AND “PET” AND “positron emission tomography/computed tomography” AND “early response evaluation” AND “treatment response” AND “outcome”.