Cancer and atherosclerosis: the broad mandate of angiogenesis.

The vasa vasorum consist of blood vessels that vary in size from vessels with single or multiple smooth muscle cell layers to simple endothelial channels. In all but large and/or atherosclerotic vessels, the vasa vasorum are confined essentially to the adventitia of the blood vessel wall.1 This microcirculatory system presumably exists for the purpose of nourishing large and medium blood vessels, including the aorta and epicardial coronary arteries. The vasa vasorum also constitute a reservoir for postnatal angiogenesis that has been studied for its potential contribution to the growth and development of neointimal thickening. It is thus intriguing to consider developing primary or restenotic lesions as relatively underperfused and, as is the model for tumor development,2 dependent for continued growth on augmented vascularization.