My 9 1/2 bitch had soft tissue cell sarcoma. It was on the lower part of her foot. While it took several surgeries, one involving some skin drafting, she is now clear. Tumor was removed and they had clear margins around it, which usually means they removed it in its entirety. Her prognosis is very good. We are also giving her homeopathic remedies and keeping a good watch on her to make sure no other lumps appear. At this time, having just turned ten, she recovered quite well.
My question would be to the vet is there any way to remove the tumor? Instead of doing just a biopsy. I hope that it works out for your dog.