tumor or abcess??

Question
QUESTION: My 1 year old female rat appears to have a fatty lump on her back behind her right leg and under her butt. Can you tell me how to tell if it is a tumor or abscess?

ANSWER:
How fast did the lump appear?  Did it seem like it just came out of the blue?  
Its hard to tell by feeling them since some mammary tumors can be soft and moveable, others can feel more firm and attached, and so can an abscess.
What to do is this:
Hold a warm wet to damp cloth on the lump for as long as she will let you. Continue to do this with the hopes of bringing it to a head. You can even gently press it once or twice around the base after doing this but do NOT continue to press it. Just once or twice is good enough. Continue with the warm compresses.
GIve it a bit of time to see if it comes to a head. If it is an abscess, it will eventually come to a head and burst, and once it is all cleaned up it will form a crater and start to heal.  A vet can always aspirate it and see what substance is inside the lump which will allow you to know right away.  
If it appeared out of nowhere, chances are it is an abscess.  If it started small about a month ago and continues to grow, its probably a mammary tumor and should be removed before it becomes vascular.

How big is it and how long has she had the lump?

---------- FOLLOW-UP ----------

QUESTION: I just noticed the lump yesterday, so it seems like it just came out of the blue but she has always been a tad on the chubby side so it is hard to tell if it has been there longer. Also it is under her inbetween her legs closer to her right leg so when she is walking it is hard to notice. The lump is about 1 1/4 inches in diameter and 1/2 inch .

Answer
Unfortunately that is in an area that mammary tumors pop up at so it could be either one.  I would try to see if it comes to a head and scabs over and HOPE its an abscess, but I would not wait too long because it can be removed easily when its small before it becomes vascular.

Here is the URL to my website about tumors and your options.

http://www.freewebs.com/crittercity/allabouttumors.htm