In the tumour environment, tumour endothelial cells express a lower level of adhesion molecules involved in leukocyte-endothelial cell interaction, such as intercellular adhesion molecule 1 (ICAM1), E-selectin, CD34, and vascular cell adhesion molecule1 (VCAM1), compared to normal endothelial cells [130]. This evidence concerns the gene CD34 and neoplasm.