Tongue cancer in a cat? I've never heard anything like that in my entire life of having cats. I've had to experience the loss of a kitty due to feline leukemia several times, but never any kind of cancer. I'm sorry for your loss, losing a constant companion and entertainment system after years of being together can be heart breaking.
When my last cat Molly, a large grey striped tabby died, it was only a week after my older sister had died of a massive infection in August of 2020. It was devastating, and I almost lost it completely. They're a part of our families, and we mourn their loss just as much as our human relatives.
I think you need to go to your local humane society and adopt an adult female kitty. They can always take her back if/when something happens to you down the road. That kind of companionship is too special to just give up.