My 20 lb, 2 year old mutt, started growing a small wart like thing on her paw a few weeks ago. It didn't grow for a bit, and then suddenly we noticed blood everywhere and looked at the growth and it had doubled in size. Vet isn't sure what it is, but wants it removed. I am thinking maybe histiocytoma, or papilloma. But can these be black? Any thoughts??

Thanks!!What is this growth on my dog's paw?-p1010243.jpg