My cat started throwing up really bad about two weeks ago. So we took him to the vet and an x-ray revealed there is a black mass growing in his stomach, possibly connected to the liver. The vet said it's likely cancerous and the only two options are to spend $3000-$4000 on surgery for removal (which there is no guarantee it'll help) or just make him comfortable at home until he passes away from it within the next few months (probably won't last the summer). He's almost 18 years old, so this is not unexpected, but should I get a second opinion. He's not the healthiest he's ever been, but his demeanor seems OK and he's eating/drinking decent. He doesn't hide anymore like he did when he was sick, so is there possibly something else I can do to prolong his life?