PDCD1 and neoplasm: Moreover, tumors were divided into three immune categories: (1) “cold tumors” with less immune cell infiltration, (2) “compartmentalized tumors” where immune cells were distributed around tumor cells in an organized regional orientation, and CD4+ T cells were mainly near PD-1+ cells in the tumor-immune border, and (3) “mixed tumors” with tumor cells and immune cells mixed together without borders, where CD8+ T cells were dominant and had relative stronger immunosuppression with worse prognosis (12).