Response rates among metastasized patients are in the range 40–50% for anti-programmed cell death protein 1 (PD-1) single-agent therapy (nivolumab or pembrolizumab) and up to 60% for combined immunotherapy with anti-cytotoxic T-lymphocyte-associated Protein 4 (CTLA-4) (ipilimumab) and anti-PD-1 (nivolumab) [28,29], thus rendering metastasized cutaneous melanoma a potentially curative disease. The gene discussed is PDCD1; the disease is cutaneous melanoma.