lump on female rat

Question
Hi, I have a female rat who is 1 year 3 months.

around 6 months ago she had a lump removed from in between her top chest. recently I have just discovered another lump on her belly near her back legs.
It's quite small at the moment and I am worried about her having to have it removed, she has been under anesthetic once already and I have heard that it is dangerous for rats to go under it more than once.

Do all tumors need to be removed or are some harmless?

thanks for your help
Sam

Answer
It doesnt matter how many times you expose your rat to anesthesia, there is a risk the first time as there is the third.  I have had tumors removed from my females two and three times with no troubles and have heard of other rats passing away during or just after surgery the first, second and even third time, prompting people to write because they are confused. They ask why did she do ok the first three times and the fourth time, she died?  It probably was not related to anesthesia at all in this case.  I always recommend blood work done prior to going under anesthesia to be sure the liver is able to handle the anesthesia and also check kidney function and heart enzymes etc....    The vet should be absolutely and totally experienced with surgery and rats.
The more skilled the surgeon is, the less risky the entire procedure is.

On a final note, you asked if the tumors are harmless.  Absolutely not. They may not always be cancerous, and in fact, only a very small percent of mammary tumors are malignant. The problem is, they grow huge and can crowd internal organs and cause problems for them to walk etc....the biggest problem is when they are vascular.  This is probably the most common cause of death from mammary tumors in rats. The tumor develops its own blood supply and starts to rob the rat of the nutrients she is getting from her food. She will eat like crazy but drop weight fast. At first its gradual, but after a while the little girl is so thin she looks like she is starving to death and malnourished.  
The best way to avoid these in the future is to have your rat spayed before she is 6 months of age.  Estrogen levels rising after menopause around 14 to 18 months of age, and sometimes older, is what triggers the growth of these tumors. Spayed rats do not have this problem and its not common for them to develop mammary tumors as they get older.

Read more about mammary tumors here on my website:

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