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Guinea Pigs/Our guinea has a movable lump on her back! :0(


We have 2 guineas, both girls and just a little over a year old - my childrens pride and joy!!One of the guineas coconut has developed a lump in her back which is pea sized. It feels soft amd is movable and she is not in any pain, is eating well and it doesnt seem to be affecting her in any way. I wondered if you might be able to give me some advice as to what this may be.

Most likely this is a sebaceous cyst. Humans get them as well. The sebaceous glands are oil glands that excrete the oils in the skin necessary to keep it soft and supple. If they plug up the sebaceous material is stuck in the gland and forms a lump.

They're not harmful or life threatening, but they will grow because the body is still producing these oils, but they can't get out of the gland so they build up. Many of them will ultimately open on their own. The material inside has the consistency of cottage cheese and usually has a very sour smell.

Sometimes they will empty themselves and then grow back again. I've opened many of them over the years and the secret to getting them to heal is to express out the goo every day until it's not longer forming.

It will not hurt the pig in any way just to leave it alone. It could stay the size that it is now, it could grow or it could open. Whatever it does it's not a malignant or cancerous cyst and will not cause either pain or discomfort to the little patient.

The interesting thing I've learned over the many years of cavies is that the substance inside is always the color of the skin under which it has grown. In other words if it's a black pig, the sebaceous material is very dark gray, in white or cream colored pigs the material follow suit.  

In abscesses the pus is always a yellow/green foul smelling fluid that is the consistency of cream. An abscess will also burst open far sooner and will not just stay as a lump. It is filled with bacteria that can be a serious threat to the health of the pig.

In the absence of a bite or wound I seldom see infectious abscesses on the back. That's why I think this is just a harmless sebaceous cyst that is fairly common even in guinea pigs.  

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Pat VanAllen


As is sometimes the case, people in urgent need of information have a higher degree of expectation than those of us as experts are able to give. The experts on this site do their best to give the most accurate and responsible answers possible. We ask that you remember that it is not our intention nor place to criticize the professional advice given by your veterinarian, nor is it appropriate for us to comment on the correctness of a diagnosis made by a licensed physician. Our knowledge is experience based. Although many years of breeding and showing cavies gives me a wealth of experience it cannot change the fact that we as experts are not veterinarians and therefore may occasionally have to reject questions that appear to be asking us to criticize advice given by the licensed professional. Having raised and exhibited cavies for many years I have extensive experience in cavy care and husbandry. I currently have an active breeding program for pedigreed show animals but do not encourage backyard breeding for inexperienced owners. Although I don't encourage breeding for fun I'm always happy to answer any questions from an owner who is in sincere need of help. Pet owners wanting to breed should understand that even experienced breeders have litter losses. The mortality rate is high in cavies. The chance for losing both sow and pups is always present, even with experience. Although this is a site for experts to assist owners, there is no expert in any field who has all the answers. The wisest thing a good expert can know is their limitations. Not having an answer does not diminish one's ability or knowledge. It simply shows that we recognize our limitations and operate within them.


Raised and shown cavies for many years, having aquired my first cavies in the early 1970's as pets. My caviary currently handles 65 + animals in two different breeds and several varieties. Having been in the health care industry as a licensed nurse for 35 years I have hands on experience with care and needs in both humans and cavies. Member of American Rabbit Breeders Association and American Cavy Breeders Association.

Awarded Lifetime Membership in of one of the oldest cavy clubs in the United States, on whose Board I served as Sec/Treas for six years and currently serving as President. Also editor/publisher of the club's quarterly newsletter. We are strong supporters of our youth exhibitors, most of whom are 4H members who are working on cavy projects. Through these projects they become good responsible citizens. We deal with all aspects of showing, breeding, caring for and sharing experiences in the fancy. The cavy fancy is not a new one but in some areas is still relatively unknown. Our goal is to inspire interest in high quality, responsible breeding to improve the species, not just the reproduction of guinea pigs. Our job is to educate owners to help them make the right decisions and choices in the care of their cavies.

Graduate in nursing. Certified in emergency medicine.

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