PDCD1 and melanoma: The success of Immune checkpoint inhibitor therapy is particularly noteworthy in melanoma, with approved treatments now encompassing anti-PD-1 agents such as nivolumab and pembrolizumab, the anti-CTLA-4 inhibitor ipilimumab, and combination therapies featuring both anti-PD-1 and CTLA-4 inhibitors like nivolumab-ipilimumab.