What can a vet do if the rat has cancer? I heard when rats start to go downhill there's very lil hope for recovery. What can the lumps be other than cancer? When at Petco I was looking at the rats and thought of getting three, then saw two others in a lil den, in the same tank. So I was thinking it's just $25 for five, but the odds are at least one of these rats will be lumpy. Do Vet consider rats as exotics and charge more?