We adopted (rescued) Molly when she was about two years old. Rather promptly discovered she had heartworm. Okay, not much you can do about that but sweat it out until the worms die, but almost all cats come through it okay, so no big deal.
Then came the first of several bouts of pancreatitis. Then a blood clot destroyed one kidney, leaving kidney function at 20% or so. Then the biggie, Lymphoma in her upper intestine. That diagnosis was almost five years ago now, and was followed by almost a year of chemotherapy.
Little bugger is still with us. We give her fluid sub-cutaneously once daily, and four or five pills twice daily. She is adorable, does not seem to mind the "abuse" in the least and loves us to death. If we leave the house she goes nuts when we return. Hangs out in my lap and purrs.
She is a little bit of a fussy eater. The medication and ongoing cancer make her a little nauseous (some of the meds are anti-nausea, and we keep adjusting those), and we have to keep finding food that she likes. But she is happy and thriving. Tough little girl.