CTLA4 and melanoma: Immune checkpoint inhibitors (ICIs) have shown antitumor activity in various malignant tumors, such as melanoma, non‐small cell lung cancer (NSCLC), renal cell cancer, Hodgkin's lymphoma, etc. ICIs include cytotoxic T lymphocyte associated antigen‐4 (CTLA‐4: monoclonal antibody ipilimumab), programmed cell death protein (PD‐1: monoclonal antibody nivolumab, pembrolizumab), and programmed cell death ligand 1 (PD‐L1: monoclonal antibody atezolizumab, durvalumab).