Tumor angiogenesis: a physiological process or genetically determined?

Continued tumor growth is dependent upon the growth of new blood vessels. This commentary reviews the mechanisms whereby tumors become vascularized and examines whether tumor angiogenesis is solely an example of a normal physiologic process or is part of the genetic program of the tumor. The likelihood that neovascularization of tumors combines both of these components, that is, utilizing tumor-specific elements as well as capacities common to all cells, is discussed.