This is in accordance with Bzyl et al. who discussed in their study with two differently aggressive breast carcinoma xenografts in mice, that the relative amount of receptor-bound MBs corresponds to immunohistochemical differences in tumor microvascular density (CD31) as well as to VEGFR2 expression concluding that BR55 reflects the VEGFR2 status in tumors and can be applied as non-invasive surrogate parameter of tumor angiogenesis [12]. Here, PECAM1 is linked to breast carcinoma.