PECAM1 and neoplasm: Tumour cells arrested preferentially in vascular branching points (Fig. 1c) and left the junctions intact in the first 4 days, as assessed by PECAM-1 (platelet and endothelial cell adhesion molecule) (Additional file 1: Figure S1) and claudin-5 immunostainig (Fig. 1d) and TEM (Additional file 1: Figure S2).