Immunofluorescent staining of excised and cryosectioned tumors (Fig. 2j) further confirmed nAlb-Cy5 accumulation at the tumor site, with the highest Cy5 fluorescence observed proximal to CD31+ tumor vasculature and with Cy5 signal also observed within the tumor stroma (e.g., colocalizing with CD45+ immune cells). Here, PECAM1 is linked to neoplasm.