PDCD1 and metastatic melanoma: Immunotherapeutics (IMTs) such as ipilimumab (anti-CTLA4 [cytotoxic T-lymphocyte associated protein 4] therapy) have yielded improved overall survival from metastatic melanoma (two large, phase III trials), and along with nivolumab/pembrolizumab (anti-PD1 [programmed cell death protein 1] therapy), comprise the cornerstone of current melanoma immunotherapy [4-5].