How to Know if it's Cancer or Large Cyst??

Ten days ago my husband was so tired of being nauseated that he agreed to go to the emergency room. After 2 cat scans and other tests the ER doc came in and said, "YOU HAVE KIDNEY CANCER." He is so sick he probably does but my daughter, a nurse, claims that "doctors don't do that. They tell you "you have a growth on your kidney and we'll have fo find out what it is. That doctor, she said , is an idiot. He never had an upper GI OR a biopsy.
  Is this true? How can they tell? Besides, a tumor that's benign is still very dangerous, right? He has been nauseated, very weak and vomiting some for weeks. His blood pressure is high and his glucose was 411 this morning before eating soup which he threw up. He has been on Levemir FlexPen for several days; he throws up about 2/3 of the time after he
gives himself the shot. He is not confused at all (yet) and is to have the kidney removed Jan 3. He won't go back to the hospital because they don't give him a THING to eat or drink and he weighs 265lb at six feet. He is 68, a type 2 .