Neoangiogenesis is very important for tumor development. Both blood and lymphatic vessels of tumor express unique markers that distinguish them from normal tissue vasculatures. According to the vascular heterogeneity and changed microenvironment, tumor vasculatures show multiple alterations and differences with regular tissue vasculatures, such as abnormal vessel wall structures, leakiness to macromolecules and constant formation and/or remodeling of vessels. Relevant studies have shown that the endothelial cells of tumor are involved in the variable expression of cell surface molecules by expressing a stimulated phenotype.

http://www.creative-biolabs.com/In-vivo-Phage-Display-for-Tumor-Targeting.htm