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Pet Rats/My poor rat has a cyst?


Mindy\'s bulge..
Mindy's bulge..  
QUESTION: HI Debbie. I am a little freaked out because today when my two rats were playing I noticed a bulge on the side of my bigger rat. Her name is Mindy. I believe she is a Fancy Mouse but I don't know much about her because they were both abandoned at the pet store about 5 months ago. I feed them three times a day. They get fruits and veggies and also take vitamins. For about a month they had to live with my friend because I was moving and I am not sure how well she took care of them. I'm not sure if she stuck to their diet... Is there a possibility that I caused my rat's cists? Could this be cancerous? I am taking her to the vet tomorrow but would like to do whatever I can to make sure she's ok. She doesn't seem to be in distress and has been pretty normal and is still eating and playful but the bulge is quite noticeable. I just would like some advice if you have any. Thank you!

A rat is a rat, and a mouse is a mouse. I need to know more about this lump before I can give you any advice. What does it feel like? Soft, hard?  Is it attached to the underlying muscle or does it feel loose?  Can you move the skin over the lump separately from the lump or does it feel like the lump is inside of or attached to the skin?  Does the lump look dark or normal skin color?  

Do you have any idea how old she is?  Did she grow after you got her?

---------- FOLLOW-UP ----------

QUESTION: Hi. I am sorry I have mice and rats and I guess I accidentally said "mouse" but I meant rat.The lump feels a little firm but soft it moves with the skin. The skin is not discolored but this lump just appeared. She has not grown since I got her. I'm sorry I didn't give more info in the beginning I was freaking out a bit. Thank you so much in advance.

No problem. Lumps within the skin, rather than under it, are more likely to be an abscess than a tumor. Cysts tend to be smaller than what I saw in the photo. See the article about abscesses on my website at on the Rat Info page.

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Debbie Ducommun


I can answer any questions about pet rats, but you will probably be able find answers to simple questions more quickly on my website at If you have a life-threatening emergency you can try calling me at 530-899-0605. I am not usually on the computer on the weekend.


I have been "The Rat Lady" since 1985 and am recognized as one of the world's experts on pet rats. I have 3 published books and already answer lots of questions about rats daily.

President of Rat Assistance & Teaching Society

I am a monthly columnist for Pet Business magazine, and my writing has appeared in other magazines. I have 3 published books.

BA in Animal Behavior

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