Dog has had a very large lump on his head since June. He has had a variety of blood test with no results.... no cancer cells. Friday he had x -rays and a biopsy. Nasty surgery to look at. Whatever it is , it is in his skull too, not just on that head bump. Cyst or tumor?- we'll find out Friday. He's 7 years old and a great dog. Sure hate to lose him.