Peritumoral vasculature is characterized by upregulated endothelial VCAM-1 expression. Representative histologic sections of peritumoral brain tissue, from breast cancer (A), lung adenocarcinoma (B), and melanoma brain metastases (C) immunohistochemically stained for the endothelial marker, CD34 (brown); scale bar = 200 μm, black dashed line outlines tumor border. D–F, Corresponding graphs showing mean microvessel density (±SD) in the peritumoral brain parenchyma in the following regions: < 0.5 mm, 0.5–1 mm, and > 1 mm from the metastasis border; n = 10 (breast), n = 9 (lung), and n = 12 (melanoma). G–I, Images showing endothelial VCAM-1 expression (arrowheads) associated with the metastasis from the same patients as above; scale bar = 100 μm. J–L, Corresponding graphs showing ratio of VCAM-1–positive/negative vessels in randomly distributed square ROIs across the peritumoral brain parenchyma. M, Representative image of endothelial VCAM-1 expression at the border of a glioblastoma, with corresponding graph of VCAM-1–positive/negative vessel distribution (N); scale bar = 100 μm.