RCA lectin in vivo labeling is an effective way to mark functional angiogenic vessels. SCCVII tumors were systemically labeled with Rhodamine-RCA Lectin and 7 μm tissue sections were counterstained with DAPI and observed under 40× objective upright microscope (Zeiss, USA) through Rhodamine and DAPI filters. (scale bar = 50 um) A: Endothelial cell nuclei staining pattern observed with bright blue DAPI counterstain in SCCVII neoplasm. B: Functional angiogenic vessels labeled by tail vein injection of Rd-RCA lectin. RCA-I is able to successfully stain endothelial cells due to the specific affinity to beta D-galactose which is found on the luminal surface of blood vessels. C: Merged signals of vessels and the cell nuclear staining by DAPI. The abundance of nuclei present in the tissue is not representative of the functional and accessible tumor vasculature in the merged image.