Background: BRAF (v-raf murine sarcoma viral oncogene homolog B1) and MEK (mitogen activated protein kinase) inhibitors, as well as immunotherapy against cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death 1 (PD-1) receptor and its ligand (PD-L1), have shown good results in improving the disease-free survival of patients with metastatic melanoma (MM). Here, PDCD1 is linked to metastatic melanoma.