Lumps and bumps on or under the skin are relatively common in rats and mice. Sometimes these masses can occur suddenly and grow quite quickly and other times they grow slowly over time.
In any case, it is recommended to book in for a vet check as soon as you notice a lump on your pet mouse or rat.
Lumps in rats and mice are most commonly caused by one of two things:
These lumps are generally the result of a bacterial infection that becomes walled off by the body and fills with pus. There are many different species of bacteria that can cause infection and the initial infection can be due to bite wounds from cage mates, self-trauma (when an animal licks or bites at themselves, often due to pain or itchiness), or any other accidental injury that subsequently becomes infected.
Cancerous lumps in rats and mice are usually of mammary origin (i.e. breast cancer) but they can appear anywhere on the body, including on the neck, shoulders, belly, flanks, tail base, groin, and armpits.
In rats, these masses are often not malignant, meaning they do not tend to spread to other areas of the body. However, in some cases malignant tumours can also occur.
The tumours most commonly appear in older female rats that have not been desexed, but can also sometimes be found in males. Tumours tend to occur more frequently in obese rats. While the tumours do not usually spread to other tissues, they can grow very quickly, interfere with the rat’s movement, and occasionally become ulcerated or infected.
Tumours in mice are also most commonly found in older females, but unlike rats these tumours are usually malignant and often spread to the lungs, causing fatal disease. Mammary tumours in mice can be associated with a virus that is passed to baby mice from their mother.
In order to find out what is causing the lump, your vet will need to take a sample of the tissue. One sampling method, called a fine needle aspirate, is performed by putting a needle into the mass and pulling out some cells to be examined under a microscope.
This may not always provide a representative sample of the mass, so further testing via an excisional biopsy may be required. An excisional biopsy involves removing the mass and sending the tissue to a laboratory for histopathology to determine the type of cells that the mass is made up of.
The recommended treatment of masses will depend on what is causing the mass, however, a general guide is below:
To treat an abscess your vet will likely prescribe antibiotics to treat the infection and anti-inflammatories to treat and pain and inflammation associated with the mass. In some cases, it may also be necessary to surgically lance and drain the pus from the abscess or even remove it completely.
The best course of action for masses in rats is usually to surgically remove the mass before it begins to limit the rat’s movement or becomes ulcerated or infected. As these masses are usually benign, surgical removal can be curative.
Predisposing factors such as obesity and hormonal factors may also need to be addressed to reduce the likelihood that the mass will return.
Unfortunately, there is often no effective long-term treatment for cancerous tumours in mice. Surgery is often challenging due to the structure and blood supply of the masses, however it can be performed in some cases.
Early detection is important, so as soon as you notice a lump on your pet you should have them checked by a vet. High calorie diets and obesity can contribute to tumour formation, so ensuring that you pet is on a healthy, balanced diet can help to decrease the likelihood of tumours developing.
Talk to your local vet about the diet that is best suited for your pet. There is evidence that desexing your rat before they are 6 months old can reduce the likelihood of tumour formation as well.
Very nice and informative service. Lovely vet practice, will definitely recommend to others.
Wonderful and knowledgable vet. Took time to thoroughly check over my rabbit and answer all the questions I had. Would recommend to other rabbit owners.
Highly recommend, caring and compassionate no matter how small your pet. Thank you to the unusual pet vets for treating our very sick little mouse Moon, she came back to full health and is now enjoying life in a new home with new cage mates.
Cannot speak highly enough of the caring and lovely staff at UPV Osborne Park. Particularly to Dr Kelly for the wonderful treatment and compassion she displayed caring for my much loved
Bugz. Definitely recommend this practice. Simply the Best.
It’s a great vet for exotic pets, we would like to thank Dr Kiara and the nurses for all the help they have done for the bunnies especially when they have been unwell.
Gretel – Thankyou for all the tips and advice on what and what not to do with the bunnies.
We will definitely be recommending to all our exotic animal friends.
Fantastic vets! Staff are so helpful and friendly. Vet’s are brilliant, they show so much love and compassion to our animals. 5 stars all the way!!
I just want to say a huge THANK YOU to the gang at Murdoch who helped my family and stimmy Cindy. It was a very stressful time and they assisted us with ease! Pricing was also more than reasonable which we were very grateful for. Thank you guys again, my noodle is now on the mend all to you guys.
Excellent service, caring and professional advice, and very good handling for our pet bird, on our first visit today at The Unusual Pet Vets, Jindalee. Very helpful, and they also provided further reading for us via email after our appointment regarding a few things we asked about. All staff were lovely and friendly – from the initial phone booking (you can do internet bookings too) to and including the consult. Thank you very much – we’ll definitely be back! Highly recommend.
Received the best service from Dr Sasha at the Sunshine Coast clinic. She taught me so much in such a kind manner and was very gentle to my Guinea pig. She then followed up by emailing further information on Guinea pig general care. Highly recommend!
Amazing and caring staff at the Ferntree Gully Clinic. Our baby rat was not well, and they always made time to help and support her. Very knowledgeable and compassionate. Would highly recommend and absolutely will use again. Thank you to everyone at Ferntree Gully for being there for us and Tabby.
