lumps (tumors?)

Question
Hi. I talked to you a while ago about my two girls, Diz and HoneyBee, who were chewing on eachother. The chewing has stopped, but not they both have developed lumps. Both have them right behind their armpits, one on the left side and one on the right. Diz's is fairly small and not nearly as noticeable, but HoneyBee's is as big as her head, if not bigger. They both let me touch them and it doesn't seem to bother them, and they are acting totally normal, but it is worrysome. They're both over a year old (I don't know how old they were when I got them over a year ago), so could it just be old age? I'm worried it might be cancer. I hardly have the money to support myself, let alone bring them to a vet, especially since it doesn't seem to be bothering them. What do you think it could be, and what should I do about it?

Answer
Hi Rachel,

The "armpit" region is a common place for mammary tumors to appear, which I'm sorry to say happens a lot more than any of us mouse owners would like.  It IS possible they just have abscesses, infections that have swelled into lumps, from open wounds obtained by chewing each other.  However, the location and the fact that both have developed them doesn't sound good to me.  I am not qualified to tell the difference in your mice, and since telling the difference decides your treatment options, I would try calling a vet and seeing if they'll at least give you any advice over the phone.  If you live near a teaching vet clinic (part of a university or vet program) they might give you lower rates.

Mice don't always show when they're in pain, but I've heard from many people that their mice with tumors went on to live perfectly happy lives.  Some tumors develop more quickly than others and will scrape against the bedding, causing discomfort, others stay the same size for the rest of their lives and don't get in the way.  I've been told that walnuts help prevent cancer occurrences, so perhaps adding walnuts to their diet and removing any corn (which is said to do the reverse) might slow down growth.  Abscesses, on the other hand, need to be lanced by a professional and treated with an antibiotic before the infection spreads.  Tumors are supposed to feel like lumps beneath the skin, that you can roll the skin over, where as abscesses are said to feel attached to the skin.  I can only recommend phoning a vet for more advice in telling the difference, though; it is simply too tough for most fanciers to figure out without licensed medical advice.

Your mice are pretty great ages for mice, so if I were you and I was sure the lumps weren't coincidental abscesses, I would just modify their diet and keep an eye on them.  They might very well just live out the rest of their lives happy and lumpy.  :)

Good luck!
-Tam

P.S. - I just wanted to add that this is an excellent article explaining tumors.  It's about rats, but it's pretty much exactly the same in mice (except surgeries on mice are done less frequently):  http://www.rmca.org/Articles/tumors.htm  This will help you understand exactly what is going on if the issue is mammary tumors.