There were newly-formed blood vessels on the surface of both fully developed malignant xenografts (after 5 weeks post inoculation) identified in situ (Figs. 3a and 4a) and from the harvested tissues (Figs. 3b and 4b), and inside the tumor masses indicated by histological H&E staining (Figs. 5a and 6a) or immunohistochemical CD31 staining (Figs. 5b and 6b). Here, PECAM1 is linked to neoplasm.