Geriatric kitty update: the tumor

Things are coming to a close for my little-old-lady-cat, Cleo. After her weight loss I started feeding her anything she'd eat and she gained quite a bit back. It wasn't until a few days later that I found a mass in her belly. A big mass.
It didn't seem to hurt her and in her fragile state I was hesitant to take her to the vet, so I called for a consult and learned it could be a tumor or an abscess. Either way it would either get way better or way worse so I decided to hold off the vet visit.
Five days later an abscess burst and she was suddenly much perkier. I took her in to the vet to have it cleaned (she fit 100ml of solution into the wound! Holy crap!) and was very saddened to learn that the abscess occurred because of s large mammory tumor on Cleo's lower teats. Because of her age (nearly 20) there is no hope in surgery. She is in mild renal failure and the vet said realistically she probably has a month, two at the most, left of life.
My poor kitty. 70-80% of feline mammory tumors are adenosarcoma (I think that's it...? I assume that's sarcoma growth of an adenoid...? No clue.) Basically it will next spread to her lungs and that will be when I have to make the final decision.
Anyway she is now home and on antibiotics for her abscess. She is comfortable, perky and very much herself. I give her subcutaneous fluids every couple of days and she seems to have clear lungs for now.
I have had Cleo since I was 6... She has been a constant in my life for as long as I remember. I'll miss her when she goes, but she has had an incredibly long and happy life.