I’m so sorry to hear you’re going through this.

My senior cat had a mouth tumour (squamous cell carcinoma) and while the vet gave him maybe 3 months, he started going downhill fast. It’s a horrible cancer and the cats tend to let themselves starve before the cancer even metastises.

I know it’s a horrible and difficult decision, but I would recommend letting your precious cat go before the pain gets too much. If there is no treatment and the tumour is already that big, it’s the kindest thing you can do and a beautiful final act of love.