Very common in rats My friend lost his to tumors So sorry I am sure whatever choice you make it is the best one for the both of you.

Tommy and I let our rat live with hers for as long as she was comfortable. She lived for over a year and a half with it after we found it. That would be my vote.

She was around 2 also. It was about marble size, under her front left leg. We always joked that it was breast cancer. It grew to be very large. At least the size of her head, if not bigger. Luckily, it wasn't sensitive, and even though it was big and cumbersome, she managed to run all around her cage, up the ramps, and even up the walls to the ceiling of it up until maybe 2 weeks before we ended up having her put down. She was overall very happy until the end. It did not compromise her quality of life.

keep us mosted on the poor thing