Previously, classical classification patterns were defined to stratify the immune microenvironment of solid tumors into four types based on the presence or absence of tumor-infiltrating lymphocytes (TILs) and PD-L1 expression, including Type I cancers (PD-L1+ TILs+), Type II cancers (PD-L1− TILs−), Type III cancers (PD-L1+ TILs−), Type IV cancers (PD-L1−TILs+) (44). The gene discussed is CD274; the disease is cancer.