PDCD1 and neoplasm: Immunotherapeutic methods, such as the immune checkpoint inhibitors targeting cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4) or programmed cell death 1 (PD‐1) / programmed cell death 1 ligand (PD‐L1), have made a breakthrough in improving the survival rate of cancer patients, which makes people pay more and more attention on the anti‐tumour properties of the immune system.3, 4, 5