An angioma is a benign tumor. This one is on a finger.
Image made by Dr. Michel Royon, apparently by using digital subtraction angiography – taking an X-ray of some body part, injecting fluorescent stuff into the vessels, then taking a second X-ray. Overlay the two images, subtract the non-fluorescent stuff, and you’ve got the shapes of the vessels, hovering in the void that was the subject’s flesh.