Oh Amy, what a startling discovery. I can imagine how terribly nervous you must be feeling. I don't how comforting it would be to tell you that we do a lot of lump removals and that mast cell sarcomas are quite common. Hopefully your vet reinforced that finding it early is really to your advantage. However, even with all the facts I know it is a scary time. Nebo is most certainly in my thoughts and prayers!