PDCD1 and lung cancer: Immune checkpoint inhibitors (ICIs), targeting the programmed cell death 1 (PD‐1), programmed cell death ligand 1 (PD‐L1) or cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4), have demonstrated impressive anti‐tumour efficacy in multiple cancers, in particular with non‐small cell lung cancer (NSCLC)7 and skin cutaneous melanoma (SKCM).8