CD163 and central nervous system cancer: Moreover, when assessed for the presence of a pro-tumorigenic M2 macrophage as indicated by CD163, a significant correlation was established between IL-33+ patient tumors and the presence of M2 macrophage phenotype (p ≤ 0.05; Fig. 2d, e, right panel) supporting the posit that glioma-derived IL-33 recruits pro-tumorigenic macrophage.