PDCD1 and melanoma: Immunotherapy using immune checkpoint inhibitors (ICIs) that mainly act on the programmed cell death-1 and its ligand (PD1/PD-L1) immune axis have been introduced as the standard of care for a variety of cancers including melanoma [7], Hodgkin’s lymphoma [8], non-small-cell lung cancer [9], renal cell carcinomas, and bladder cancer [10].