There are no blood vessels in the cornea. Observed blood vessels growing from edge of eye toward tumor. Endothelial cells divide 48 hours after exposure to taf. Normally the endothelial cells divide less frequently than skin cells. Skin cells divide once every 50 days.
Endothelial cells produce buds off existing blood vessel near the tumor.
The basement membrane has collagen fibers that are hard to get through. What has been observed is that tumors break through the basement membrane at about the same time as they get vascularized. Either the endothelial cells could be breaking through the membrane first or the tumor cells could be. We have a gene for taf in our cells. During embryonic development you need blood vessels to grow.