Five-year-old gerbil looks like it has a "tumor" growing on belly, where hair line is. "tumor" is reddish-pinkish, size of a half-thumbnail and round with a black dot about 2 mm in circumference. Not looking to do chemo on a gerbil, but does this sound like anything else? Thanks

Optional Information:
Age: 5; Male; Breed: gerbil

Already Tried:
Nothing, just appeared over last week or so.