Analysis of the expression of ACVRL1 and ENG, either alone or combined, in 20 human PanNETs and 9 metastases (cohort previously reported in [17]) was demonstrated to be highly correlated to an endothelial cell metagene consisting of CD34, CDH5 and PECAM1 (Figure 1A–1C), indicating an exclusive endothelial cell expression within the tumor neovasculature. Here, PECAM1 is linked to neoplasm.