a large lump on my rat): is it a tumor?!?!?

Question
Today, while giving my rat, Jimmy, a bath, I noticed he had a lump on my lower back/butt area on the right. It's about the size of a dime and it is raised about a quarter of an inch. Its completely red. He is acting normal and such, although he is less active and sleeps more now. I bought him in 2009 in September, so hes a little old. Hes also a fancy rat, just to let you know. He isnt really sensitive when I touch his lump. What do you think the lump is? And can you let me know what I should do to make it go away? I am planning on taking him to the vet on monday for a check up, thanks!
~Amanda

Answer
It could be a tumor or it could be an abscess.  If it doesnt have a scab on it, it is probably a tumor/mass.  This does NOT mean its cancerous, however.    

Also, be sure the vet your seeing has experience with rats.  Please refer to my personal website, sandyscrittercity.com and check out the info on rat tumors and also about how to know if you have a good vet for your rat.  

You can go private and tell me the vets name and I can let you know if they are right for your rat if you have never seen this vet before.