PECAM1 and neoplasm: Indeed, leukocytes require a number of molecules in order to roll, adhere, and finally transmigrate into the tumour microenvironment, including selectins, PECAM-1, intracellular adhesion molecular-1, -2 (ICAM-1, ICAM-2, respectively), and vascular cell adhesion molecular -1 (VCAM-1), amongst others [172].