More About Angiogenesis
A tumor consists of cells that are dividing at an abnormally high rate, crowding surrounding healthy cells and competing for resources. Tumor growth typically proceeds in 3 dimensions, pushing out from the surrounding normal tissue and growing to become visible to the naked eye. A tumor must recruit blood vessels from the surrounding tissue to grow much bigger than 1 mm across(see the VEGF animation).
Cancer occurs when a single cell acquires the ability to reproduce aggressively and to invade other tissues. This rebellious cell shuns its normal role, instead multiplying and ultimately colonizing areas of the body where it doesn't belong. Left unchecked, this anarchy destroys the cellular society. It interferes with the body's normal function, destroys organs, and eventually kills the organism.