I am very sad to report that we lost our dog Leo to cancer last Thursday Actually, we are not quite sure - he stopped eating and after several trips to the vet and all kinds of tests (x-ray, ultrasound, blood panels, antibiotics, then meds for stomach upset, predisone, etc. etc) they found ulcers in his mouth. One rather large ulcer was removed and sent in and the diagnosis was melanoma. The mouth/ulcers were healing up with treatment and he should have started to eat, but he would not.
He was restless, skittish, and without energy, and of course lost a lot of weight very rapidly. Our vet referred us to a clinic with specialists who were unable to find anything definitive that would explain why he was not eating, and rather that starting with MRI and endoscopy etc. we decided to let him go. He was so miserable and seeing him not getting better at all, we did not want him to have to suffer any longer.