PDCD1 and melanoma: Since the first approval of ipilimumab for melanoma in 2011, six anti-PD-1/PD-L1 antibodies and one anti-CTLA-4 antibody have been approved, and ICI have reshaped the standard of care in solid and hematological malignancies, yielding unprecedented results in an unparalleled wide range of indications [48], as recognized by the 2018 Nobel Prize award for Medicine and Physiology.