# tumor on an aged female mouse



## mr.finkelmaus (Aug 10, 2009)

i just found one of my female breeder mice with a round bump on her left side. i heard from other mice keepers that it is very common for old female mice to develop tumors. i want to know if she's in pain or should i just let her die naturally? also, when they develop tumors, does that mean their breeding abilities are over. i just want her to be comfortable in her old age. i hope you have answers to my questions. thanks.


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## Jemma (Mar 11, 2010)

As I understand it, tumours have implcations for breeders because the propensity to develop them can be genetic.

I've plenty experience with poorly bred mice developing tumours, unfortunately. If I'm sure it's a tumour (not an abscess or anything like that), I just leave it until it starts having a negative effect on the mouse's quality of life. They can manage surprisingly well with a tumour, unless it's in an awkward place - just watch out for any behavioural changes or her losing condition or mobility. Some tumours grow really quickly, others much more slowly.


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## arliejacobs (May 29, 2010)

If mice are anything like rats regarding tumours, it sounds like she has a mammary tumour. Our rat, Oreo, got one at 16 mos old. She lived for 5 mos. It got extremely large and made it very difficult for her to get around. We put her to sleep on April 1. I don't know what the timetable would be for a mouse though.


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## Jack Garcia (Oct 9, 2009)

A lot of female mice (and rats) get tumors after age one year or so. Breeders can select against it to a point, but only a point. You have to consider that in the wild, a year-old mouse would be extremely elderly and her body would be shutting down naturally. We can extend their lifespans somewhat in captivity, but not unrealistically past what nature has given us to work with.

Mice with tumors _can_ get pregnant, but they often die during pregnancy, birth, or nursing. The female hormones that surge through the body while pregnant also feed the tumors and cause them to grow even faster. Sometimes their body recognizes the threat of cancer and spontaneously aborts the litter. I think I had this happen once with a mouse who had vaginal cancer. Even among people, cancer during pregnancy is a very controversial women's health issue because it usually means sacrificing the life of either the mother or the offspring, or both. It is very, very dangerous.


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## moustress (Sep 25, 2009)

You've got it all wrong, Jack. It's the estrus cycle that stimulates the cancererous tumors. Pregnancy stabilizes the hormonal levels through pregnancy and continuing into nursing. Does that have not been bred have a much greater chance of getting of mammary tumors, especially after one year of age. This phenomenon also applies to human females; the greater the number of months spent pregnant and nursing, the lower the chance of breast cancer.


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## Jack Garcia (Oct 9, 2009)

Guess I might. If nothing else, greater nutritional requirements of pregnancy also lead to more resources for tumors.


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## SarahY (Nov 6, 2008)

> You've got it all wrong, Jack. It's the estrus cycle that stimulates the cancererous tumors. Pregnancy stabilizes the hormonal levels through pregnancy and continuing into nursing.


I could not _imagine_ putting an animal with a tumour through raising a litter! I cannot see why anyone would want to! I certainly wouldn't fancy nursing a baby with a humungous tumour in my boob. I've known tumours go from being pea sized to ping pong ball sized in a matter of days, it seems to me that breeding a mouse with a tumour is just asking for a painful ordeal for the doe and an orphaned litter. Tumours suck the resources and energy out of a mouse like nobodies business.

Sarah.


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## Jack Garcia (Oct 9, 2009)

That's right, Sarah.

I had cancer when I was 22. Believe-you-me, it's stressful enough by itself without the added stresses of pregnancy, birth, and nursing.


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## SarahY (Nov 6, 2008)

Do you generally find pregnancy, birth and nursing very stressful then, Jack? :lol: :lol:

Seriously though, I am very sorry to hear you had to go through having cancer 

Sarah xxx


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## Jack Garcia (Oct 9, 2009)

Haha! :lol:

I'm very lucky and all better. I had one of the most curable kinds (follicular carcinoma of the thyroid gland) and after surgery and radiation I've been in remission for years. Mice are unfortunately not as lucky since their most common cancer (mammary cancer in females) is only sometimes operable and often grows or re-grows much, much, more quickly than the kind I had.

When a mouse of mine gets cancer, it is never bred from again, period. Not only because it might (or might not) be inheritable but also because of all the stresses any type of cancer puts on the body.


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## moustress (Sep 25, 2009)

A doe I purchased several years ago as an adult developed a tumor a few weeks after first litter was weaned. I bred her again, and her tumor disappeared; I left the buck in with her through the pregnancy and she conceived again. She got a six week rest, the tumor reappeared, and I put her with the buck again. The tumor disappeared once again. This was her last litter. the pregnancies prolonged her life by suspending the estrus cycle. Noe of her offspring ever had a tumor, but then, they were on a corn free diet. I find it odd that other breeders resist the idea of using the corn free diet when it so obviously improves the health of the meeces.

I normally only allow a doe to have three litters before retirement, this was the only exception I have made to that rule. Not all does have more than one litter in my mousery, indeed most of them are never bred at all.

I want to add here that treatment of human cancers of breast and prostate cancer((and probably other genitive cancers) use a drug that totally suppress testosterone, estrogen, and progesterone because these cancers are stimulate to grow by the hormones.


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## WillowDragon (Jan 7, 2009)

moustress said:


> You've got it all wrong, Jack. It's the estrus cycle that stimulates the cancererous tumors. Pregnancy stabilizes the hormonal levels through pregnancy and continuing into nursing. Does that have not been bred have a much greater chance of getting of mammary tumors, especially after one year of age. This phenomenon also applies to human females; the greater the number of months spent pregnant and nursing, the lower the chance of breast cancer.


I am a great reader of 'real life story' magazines... in britian we have mags such as Chat, Take a Break etc etc... every story I have read about a mother to a young child, or about to give birth who suffers from cancer (And unfortunately there have been ALOT over the years) actually states the opposite to what you said there moustress, the pregnancy actually excelerated the growth and spread of thier cancer.
Though from the different things I have read via the internet, it does suggest that pregnancy hormones and delivery have different effects on different cancers. I have read several studies about how pregnancy excelerates stomach, breast and brain cancers. Though scientists are researching the theory that pregnancy and birth may help prevent cervical cancers.

Though I profess I am by no means an expert when it comes to cancers in mice, happily I have not seen much of it in the mice i have kept over the years. More so in rats really.
Though I have found that reading up on human studies can correlate somewhat with the same sort of illness in mice.

W xx


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## Jack Garcia (Oct 9, 2009)

Thanks, y'all.


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## neurozool (May 22, 2010)

*hugs* Jack!

And Willow and Jack are correct, pregnancy will accelerate tumor growth and take months off the time that mouse has to live. What you most likely had was not a tumor, but an abscess that was draining on it's own, and then coming back. The timing was most likely coincidence. Not only that, but breeding a mouse that has cancer is cruel to that mouse, and cruel to the babies- if you thought that mouse had cancer, then by breeding it, you were taking a gamble that the pups would get cancer young and die. What would make you take a risk like that?? If you get cancer in a mouse under a year, they should not be bred, and you should give serious thoughts to ending that line completely, or if able, backtracking to restart the line with a related mouse that has shown no signs.

I think what you are referring to in regard to cancer and pregnancy is not that it will stop tumor growth, but that an early pregnancy decreases the chances of them *getting* cancer. This has been proven in lab mice, but *not* that a pregnancy will stop or delay tumor growth.


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## Cait (Oct 3, 2008)

Jack, sorry to hear about what you went through. Glad you're well now though 

I don't feed a corn free diet and have few tumours in my mice - the ones I do are in old does. As someone posted on another thread, supposedly it's the mould/fungus/bacteria that can grow on improperly stored corn that causes the problems, not the corn itself. Therefore if you feed good quality well stored dry corn presumably there isn't much of a risk.


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## neurozool (May 22, 2010)

Well, I have 3 mice that developed tumors at 8 months and they had *never* had any corn- so while that is most likely a big piece in the puzzle for many tumors, I think many more are genetic and good breeding practices can eliminate those tumors. But like Jack said, you can only go so far with this. In old age, it's all up in the air.


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## Wight Isle Stud (May 19, 2010)

Try this. If you have a strain of mice that are likely to develop tumours, and you wish to continue them, do not let the babies get any milk WHATSOEVER from their natural mother, foster the babies out straight away. You will find that the incidence of tumours drops to non existent. yes, its very difficult to do as we can never really tel when a doe is gonna drop, but if we have a few does drop at once, three fosters and one suspect strain, most of the pinkies will feed off of a foster as they do, some wil get milk from the mother but you will of at lease acheived something.
It works. You will eventually be hard pushed to remember when you last had a tumour in the strain.


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## SarahC (Oct 3, 2008)

I'll be back. said:


> Try this. If you have a strain of mice that are likely to develop tumours, and you wish to continue them, do not let the babies get any milk WHATSOEVER from their natural mother, foster the babies out straight


What a good tip.Sometimes the obvious needs pointing out.With mammary tumours in mice being linked to a virus it's definately worth a try.I've eliminated tumours by constant culling but it's disappointing to cull individuals that you want to hang on to.


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