PDCD1 and melanoma: The development of immune checkpoint inhibitors, targeting PD-1 (programmed cell death-1), such as nivolumab and pembrolizumab, or PD-L1 (programmed death-ligand 1), such as atezolizumab and durvalumab, has dramatically changed the therapeutic scenario for several types of cancer, including melanoma, lung, breast, kidney and bladder.