CD8A and neoplasm: Cytotoxic CD8+ T cells and CD4+ T helper cells are involved in anti-tumourigenic functions, while regulatory T cells (Tregs) contribute to pro-tumourigenic functions.9, 10, 11 Depending on the presence and location of T cells, tumours are either classified as immune-infiltrated-inflamed (hot), immune-excluded or immune-desert (cold) tumours, which has been referred to as the tumour immune phenotype (Figure 1).