my sympathies - we are going through the exact same thing with our african pygmy hedgehog...he has several tumors, although most are probably benign, but he is in good spirits and isn't on his last legs yet, so we're enjoying our time with him and feeding him lots of treats...
i know how hard it is to let go, but keeping kitty free from suffering is infinitely more important...
again, my deepest condolences.
/sniffing right now...