Cancer almost always shows up in blood work, so I'm going to remain optimistic that she just has something else affecting her appetite that the Pred will take care of. Prayers coming my way for your precious Sydney! One time, my orange kitty, MacGyver, has a mystery illness that the vets, even the specialists, could not diagnose. They wanted me to spend thousands of dollars to find out. I couldn't afford that (I understand your situation very well), so I just asked for some special food I could force feed him to put some weight on him, some Sub-Q fluids so he wouldn't dehydrate, and some antibiotics on the hunch I had that he had a blood infection. Well, 24 hours after leaving the vet, Mac started to eat and drink on his own. That was four years ago and he is now a very healthy 11-year-old cat. Miracles do happen!