Especially, immune checkpoint inhibitors targeting the programmed cell death (PD-1)-programmed cell death ligand (PD-L1) axis, as well as those targeting the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and the lymphocyte-activation gene 3 (LAG-3), now play key roles in the management of a range of advanced skin cancers including melanoma, Merkel cell carcinoma, basal cell carcinoma, and squamous cell carcinoma [1,2,3,4,5,6,7]. Here, PDCD1 is linked to melanoma.