PECAM1 and central nervous system cancer: To explore positive expression markers and further investigate cellular identities in MNOs, we performed immunohistochemical analyses using a variety of cell type markers, including CD31 for endothelial cells, CD68 and Iba1 for macrophage/microglia, CD3 for T cells, Olig2 and SOX2 for glioma stem cells, PanCK for epithelial cells, and GFAP for astrocytes.