You probably did the best thing by taking your cat to a specialized center where they deal with cancer alot. When Nicholas had surgery for mast cell tumor, a wide enough margin was taken. I bet they did the same thing when your cat had the surgery. But, it is scary and it is hard to believe that that could happen to your cat. And waiting for the biopsy result will seem like forever!! Just hug your cat! He must feel pretty good if he is that active!! Take care...