# Why are rats and mice so prone to tumors?

**URL:** <https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212>\
**Category:** Factual Questions\
**Created:** [December 12, 2015, 1:05am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212 "2015-12-12T01:05:20Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Brodi](https://avatars.discourse-cdn.com/v4/letter/b/cc9497/32.png) [@Brodi](https://boards.straightdope.com/u/Brodi)\
**Post date:** [December 12, 2015, 1:05am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212/1 "2015-12-12T01:05:20Z")

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Why are rats and mice so prone to getting various tumors? Is their (average pet store mouse or rat) gene pool really shallow? Is it some kind of “Founder Effect” going on?

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**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\
**Post date:** [December 12, 2015, 1:09am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212/2 "2015-12-12T01:09:38Z")

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Some factors:

They are supposed to not live very long in the wild. Raising them as pets prolongs their lifespans and it’s likely to happen in older animals.

In my experience, and IIRC according to a vet, females are more prone to tumors than males.

Note that these tumors are often benign, and don’t require treatment unless they interfere with locomotion.

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [December 12, 2015, 3:07am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212/3 "2015-12-12T03:07:00Z")

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> [@Brodi](#):
>
> Why are rats and mice so prone to getting various tumors? Is their (average pet store mouse or rat) gene pool really shallow? Is it some kind of “Founder Effect” going on?

[some of them are specifically bred to be cancer-prone.](https://en.wikipedia.org/wiki/Oncomouse)

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**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\
**Post date:** [December 12, 2015, 5:28am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212/4 "2015-12-12T05:28:48Z")

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I don’t know that particular strain but there are others, e.g. Lewis, and most are white/albino. Pet rats are sometimes white but more often not. So there’s little confusing the two, andPet mice might be white.

And of course, pet mice are unlike to [cost $275](http://www.taconic.com/mouse-model/floxed-p53-mouse)…

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**Author:** ![snowmaster](https://avatars.discourse-cdn.com/v4/letter/s/e99b99/32.png) [@snowmaster](https://boards.straightdope.com/u/snowmaster)\
**Post date:** [December 12, 2015, 9:51am UTC](https://boards.straightdope.com/t/why-are-rats-and-mice-so-prone-to-tumors/740212/5 "2015-12-12T09:51:42Z")

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The leading cause of cancer in lab rats is research 😉