Based on the status of pre-existing TIL, tumor microenvironments are classified into three types: (I) immune inflamed type, where dense functional CD8+ T cells infiltrate; (II) excluded infiltration type, where abnormal angiogenesis and immunosuppressive reactive stroma prevent the infiltration of T cell; (III) immune ignorance type, where tumor mutation burden and the expression of antigen presentation machinery marker are low [24]. The gene discussed is CD8A; the disease is neoplasm.