The detailed ultrastructural survey of 18 <i>IDH1</i> -wildtype glioblastomas (GBM) and 12 <i>IDH1</i> -mutant High-grade gliomas indicated that tumor vessels of both types had undergone deformities such as the thickening of the vessel wall (VW) and proliferation of the basement membrane, contour distortions, abnormal and discontinuous basal lamina, tumor cells' invasion and colonization of VW, disappearance of endothelial cells (ECs), pericytes, and smooth muscle cells, as well as the formation of a continuous ring of tumor cells attached to the luminal side of VW in numerous cases. The gene discussed is IDH1; the disease is neoplasm.