CD34 and breast cancer: Although the histology of DMBA-induced mammary tumors from animals administered YC-1 did not differ greatly from those given vehicle, immunohistochemical analysis showed a significant reduction in VEGF staining in tumors obtained from YC-1 treated animals (Fig. 4B, upper panel), together with a corresponding decrease in CD34 staining (Fig. 4B, middle panel), suggesting a reduced number of blood vessels.