PDCD1 and melanoma: The introduction of immune checkpoint inhibitors (ICIs) in the treatment of advanced melanoma represents one of the most striking advances of recent decades.[1] ICIs are monoclonal antibodies that target the immune checkpoint molecules that exist on the surface of immune cells and regulate their activity.[1] Currently approved ICIs for melanoma are ipilimumab that targets cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and nivolumab and pembrolizumab that target programmed cell death protein 1 (PD-1).