PECAM1 and neoplasm: Tumours in the HP-13C-MRI cohort had a significantly higher CD31-derived microvessel density (MVD) on immunohistochemistry (IHC; P = 0.034; Fig. 2i), which was associated with a significant increase in tumour-derived Ktrans (P = 0.003; Fig. 2j), a 1H-MRI-derived measure of vascular perfusion and permeability acquired after the intravenous administration of contrast media38.