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Pet Rats/tumor in male rat


I have a 2 year old male rat.Last month he had surgery to remove a tumor,it was on his side by his rear leg. He recovered well from surgery but last week I noticed he has another tumor growing.This time it also has a red bleeding sore.The vet is an exotics vet but has not been able to give me any definite answers. We dont know if it is malignent or benign. A cystology was done by aspurating with a needle but it did not give us any info.I just thought tumors were rare in males. The vet pointed out his mamarry gland was near the tumor site but could not say whether thats whats causing this. Im just wondering if we put him through another surgery if the tumor will just grow back again? Any thoughts? Thanks so much, irs frustrating because its so hard to say for sure what the outcome will be.


Thank you for your question.

Tumors are one of the most common health problems in rats. Benign tumors are usually separate from tissue (move around under the skin). Most mammary tumors are benign with the exception of the ones located around the vulva or anus area.  Malignant tumors are usually dark and can include symptoms such as a skin ulcer, infected lump or abscess that won't seem to heal, an ulcerated or bleeding tumor, weight loss and lethargy to name a few. A benign tumor won't develop an ulcer until it is very large. Both males and females are susceptible to tumors, unspayed females just being more so. Males can get mammary tumors as well but they are uncommon and are almost always benign. A needle biopsy is usually not helpful in the diagnosis of the type of tumor.

Based on the location of your rat's tumor (the side), I would suspect a fibroma. These tumors derive from fibrous tissue, are quite hard, and are found on the sides or back of the body. Fibrosarcoma is another common tumor found on the leg or sometimes on the side.

I hope that helps and gives you something you can discuss with your vet as to the best method of treatment moving forward. Good luck! I too am in a similar situation- my heart rat just had a mammary tumor removed from her front armpit and now my husband's heart rat has developed a similar type lump on her belly, just above her hind leg.  

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Shawna Laufer


Nutrition has always been an interest of mine as well as creating stimulating environments for rats. I conduct product reviews on my blog so I can take questions regarding products marketed or intended for rats. Other questions regarding basic husbandry, feeding, grooming, and other pet rat care will be accepted. I have very little breeding experience so I would not be able to answer much in the ways of breeding or genetics questions. I can help with some basic health care questions but am not a vet and always suggest contacting your vet for serious inquires.


I have over 13 years of experience with pet rats, having worked in several pet stores, as a veterinary tech assistant, and with my own pet rats. I run a highly regarded blog on the subject of pet rat ownership ( with a corresponding YouTube channel and Facebook page. I have been and always will be open to questions and comments.

A photograph of my lady rat's cage is being published in Worth Publishers' college textbook "How Children Develop, 4e" by Robert Siegler, Judy DeLoache and Nancy Eisenberg on the subject of how complex, stimulating environments and how they relate to the brains of rats.

I have some college experience, but not in the field of animals. I completed the majority of an at-home Veterinary Technician course which I was unable to complete due to financial reason. The majority of my knowledge on rats have come from personal experience, conducting my own research with the help of published medical studies and journal, the internet and through other knowledgeable 'rat people'.

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