PDCD1 and neoplasm: The fact that the immune system has the potential to control and/or eliminate cancers even after they have become clinically evident is based on immunotherapies such as checkpoint blockade, where patients are treated with antibodies that block negative regulatory molecules such as PD-1/PD-L1 or CTLA4, which normally restrain T-cell responses, strengthening patient’s anti-tumor T-cell responses, shrinking tumors or even curing some patients.