GFAP and glioblastoma: Per histopathological grade a significantly increased relative number of GFAP+CD16+ monocytes was found compared to healthy controls in diffuse astrocytoma (P < 0.005), oligodendroglioma (P < 0.001), GBM (P < 0.001) and brain metastasis (P < 0.001) (Fig. 2A).