mammary tumors?

Question
I have a female hairless rat. She is 1yr 4m old. When she was about 9-10 months she had a mammary tumor. We had it removed and the surgery went well. She now has another right under where the last one was (under armpit). Would you still recommend surgery now that she is older, or would you try tamoxofin to see if it will stop growing or shrink. It is not very big at this point. Any ideas or thoughts would be greatly appreciated, esp. since finances are very tight right now. Also her cagemate died yesterday - will that affect stress level or play a factor in making a decision now.

Answer
 Being close to a year and a half she isn't really that old, even poorly bred pet store rats tend to live at least to two, though it is a bit disconcerting that she got a tumor at only 9 months.  Rats usually do pretty well in surgery as long as they are in good health otherwise and surgery has the best chance to work.  Once rats get tumors, though, they usually continue to get more, sometimes, as you have seen, in the exact same spot.  It's an unfortunate side effect of our pet rats being descended from lab rats where they were bred to have cancer.

 I'm not too sure of the efficacy of Tamoxifen or what the cost would be compared with surgery so I can't really tell you either way which would be the best course of action.  I would talk to your vet and see what kind of success they have had with Tamoxifen and discuss whether or not that would be a viable option.  However, if it the chemotherapy is cheaper you will still have to pay for multiple treatments and in the long run, unless it works very very well, you may end up spending more than the surgery would have cost.  If the tumor isn't growing at a tremendous rate you may be better off just saving money in preparation for a surgery later on, though then again if you wait too long she may be too old and feeble to survive the surgery.

 The death of a cagemate can affect the stress of a rat, but sometimes they can be perfectly fine.  Keep an eye on her to see if she is acting normally.  Usually grieving rats may act more sleepy than usual and be less active, perhaps even eating less food.  Some rats deal with it better than others, so you'll just have to watch her and see how the death affects her.

 Well whatever your decision I hope everything turns out all right for your girl!  Good luck!