IL4 and neoplasm: Interestingly, high PD-L1 epithelial expression was significantly correlated to low TSR (high stroma percent) (p = 0.012) and this was explained as high stroma might promote PD-L1 expression by tumour cells through releasing proinflammatory molecules or cytokines, such as (IFN)-γ, IFN-α, IFN-β, tumour necrosis factor (TNF)-α, epidermal growth factor, interleukin (IL)-17, IL-4 and IL-27 [37].