Figure 1.

Diverse size and morphology of blood vessels in MCa-IV tumors. A: Hematoxylin-and-eosin-stained 2-μm methacrylate section showing irregularly shaped blood vessels (arrowheads) emptied of blood by vascular perfusion and surrounded by sleeves of tumor cells (arrows) interspersed by necrotic tissue (*). Region in box is shown at higher magnification in B. B: Irregular luminal lining layer (arrowheads) of vessel surrounded by tumor cells. Necrotic tissue is present at the bottom (*). C: Scanning EM view of 100-μm Vibratome section of a subcutaneous MCa-IV tumor with skin at the top. Blood vessels appear as black holes (arrows). Necrotic tissue is pale (*). D: FITC-labeled L. esculentum lectin (green) marks blood vessels in 100-μm section of tumor with overlying skin at the top. Extravasation of lectin, which makes vessel borders appear fuzzy (arrowheads), is most conspicuous in the tumor’s highly vascular capsule (arrows). E: Fluorescent cationic liposomes (red) mark the same blood vessels as those labeled with lectin in D. Vessel borders (arrowheads) are more clearly defined than with the lectin because of the lack of extravasation. Capsule, arrows. F: Brightfield image showing CD31 immunoreactivity in 100-μm section of tumor. Both blood vessels (arrows) and tiny sprouts (arrowheads) have CD31 immunoreactivity. Densely vascular capsule (double arrows). G and H: Region of tumor with a wide range of vessel size (arrows) shown by green lectin colocalized with red cationic liposomes. I: Tumor with CD31-immunofluorescent blood vessels (arrows), tiny sprouts (arrowheads), and densely vascular capsule (double arrows). Necrotic region (*) has nonspecific fluorescence. Scale bar in I applies to all figures; bar length represents 300 μm in A, D, E, and G–I; 80 μm in B; and 400 μm in C and F.