PD-1 expression on NK cells is upregulated in several cancers, including head and neck cancer (69), thyroid cancer (87), Hodgkin lymphoma (HL) (88), digestive cancers (esophageal, liver, colorectal, gastric and biliary) (89), breast cancer (93), NK/T cell lymphomas (119), Kaposi sarcoma (90), renal cell carcinoma (91), and multiple myeloma (92). This evidence concerns the gene PDCD1 and Hodgkins lymphoma.