CD274 and neoplasm: Specifically, it is based on the PD-L1 expression and TIL density, consisting of the following four types: type I (PD-L1+/TILhigh), type II (PD-L1−/TILlow), type III (PD-L1+/TILlow) and type IV (PD-L1−/TILhigh).41–43 According to this classification, the type I tumours are the most susceptible to anti-PD-1/PD-L1 blockade, because they have sufficient pre-existing TILs that are inactivated by PD-L1 upregulation.