my mouse Doe has a small pink lump on her back and we are quite sure that it is not a tuma and we wanted to no if anyone new what it could be she dose not seem to have changed in behaviour and is still eating well
If you'd like to find out what it is, you can do a simple test.
Take a surgical needle, about 18gage (you can probably find these are the feed store, or a hospital if you have a nurse friend who can sneak you some!), and probe the mass. Only stick the needle in enough to puncture the mass.
It's easiest to pinch the mass between your fingers, while someone else holds the mouse's body, then stick in the tip of the needle.
If you get a little blood, or no blood, it's possibly a tumor, and you should have it checked out by a vet, or put the animal down. If you get white goo, it is likely a cyst, or infection, which you can squeeze slowly to drain, and then treat the mouse with anti-biotics. If you get a large amount of blood, or a large amount of dark blood, it may be a blood clot, or hematoma. I am not sure what to do about these, unfortunately.