CD274 and cancer: Teng and colleagues suggested 4 cancer subgroups based on the following criteria [70]: 1) type I (adaptive immune resistance) characterised by presence of both PD-L1 and TIL; 2) type II (immunological ignorance) characterised by the absence of both PD-L1 and TILs; 3) type III (intrinsic induction) which showed expression of PD-L1 in the absence of TILs; and 4) type IV (tolerance/other suppressor pathways) characterised by the presence of TILs, in the absence of PD-L1 expression.