Mouse Tumor

Mouse tumors

Unless you are 100% certain that the mouse has a tumor, ask your vet to check. Sometimes abscesses are mistaken for tumors, and prompt treatment could be important. Mice are prone to mammary tumors, which occur most commonly in the armpit, along the sides and on the abdomen, and sometimes on the back of the neck.

Mammary tissue can be found in places you might not expect! Tumors start as a small lump and grow into larger lumps, some lumpy and some smooth. Generally the tumors that feel like smooth balls of fat under the surface, and which are not tightly attached to the underlying tissue, are the least serious and are easiest to remove.

True tumors will not go away on their own, and there is at present no real ‘cure’ except surgery, although you can do other things to improve the quality of life – see steroid treatment below. Your vet may be able to operate to remove a tumor, but bear in mind that a secondary tumor often grows within a few months of surgery.

If you decide not to operate, mice can live very happily even with large tumors for some months. If the tumor starts to ulcerate it will become sore and raw on its surface; at this stage, either removal or euthanization is necessary. Steroid treatment can make the mouse’s last few months more comfortable.


  1. Rosalba D'agostino on January 28 at 3:47 pm

    hi, today i was change my mice cage and i find my female mice with a larger lumps in one side to her abdominal,i se her walking strange with something bending under in one side her leg and when i pick her up i see a larger lumps lumpy. I want take her to the vet from remove that lumps but the vet is too far from where i live. I want know what i can do for my mice,someone can give the advice? because i can see my mice like that and also she suffer in this condition. Please, help. Rosalba.

  2. Rosalba D'agostino on January 28 at 3:53 pm

    Hi, someone can answer on my comment ? i need help and i can t see my female mice like that. Please, HELP!!!!!! thanks. Rosalba.

  3. Charlotte on February 14 at 2:46 am

    Rosalba, take your mouse to the vet! It is cruel to let it suffer!

  4. Racqueal on October 3 at 10:16 am

    Today I was holding my male mouse peanut. And I notice he has kinds a small lump were his back leg is I don’t now if its a tumor or his leg bone sticking out help

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