I'm sad for you to be faced with this decision. We had a beagle mix put down a few years ago. He, too, was diagnosed with cancer and he had multiple small tumors on his chest. Our vet told us when we noticed his quality of life decrease it would be time to say goodbye. We knew when he wasn't interested in food anymore (he was a beagle, after all :) ) he was done fighting. I'm with Vida, is it possible to have the tumor removed? What does the vet say now that it's bigger and has an open sore?
Angel, I'd still be sour at your dad's b****, too! Poor Zukie. :(
Stella - sweet, timid, elegant, lovely, lively, amazing
Luna - large, unattractive, naughty, adored