PECAM1 and glioblastoma: The differences in expression of endothelial markers (CD31, CD34, vWF) together with markers of active endothelia (CD105), proportions of newly-formed microvessels (ratios CD105/CD31, CD105/CD34 and CD105/vWF), intratumor hypoxia (HIF2α), angiogenesis (VEGF), and proliferative activity (Ki-67) were examined between GBM samples with IDH1 R132H mutation by comparison with IDH1 wild-type tumors.