Perfusion through VM vessels was also inferred by intravenous injection of tomato lectin into mice harboring CDX09 tumors, which labels glycoproteins lining the inside of functional vessels carrying blood.38,39 IF for intravenous tomato lectin (pink) and CD31 (yellow) within CDX09 tumors (Fig. 1C and Supplementary Fig. 2) revealed perfused, hollow VM vessels (tomato lectin+/CD31−) (pink arrow) lined by human tumor cells and perfused, hollow endothelial vessels (tomato lectin+/CD31+) (yellow arrow), providing evidence that VM vessels that support blood flow are present in CDX tumors. Here, PECAM1 is linked to neoplasm.