CD68 and neoplasm: Because the main cellular components of the glial scar are astrocytes, microglia, and NG2 glia, which constitute an important part of the microenvironment for host-tumor interaction [42], we examined the effect of F3.CD-TK therapy on the polarization state of microglia (i.e., CNS-resident macrophages immunopositive for CD68+) [44] inside the host tissue 200–400 μm away from the interface midline via calculating the ratio of M1/M2 microglia (M1: CD86+/CD68+: pro-inflammatory and cytotoxic; M2: arginase+/CD68+: anti-inflammatory and immunomodulatory) [45].