Causes and Prevention of Cancer in Dogs and Cats The Types and Causes of Cancer in Pets

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Cancer in cats and dogs can be caused by several different factors, or the cause could be unknown. Here are the common causes of cancer in pets, and prevention methods.

After a cancer diagnosis, it is only natural for pet owners to want to try to understand why their cat or dog would be struck with this terrible disease. As with cancer in humans, it’s difficult to pin down why some pets get cancer, and others do not. The causes of cancer are not totally known, although there are some factors that have been identified as playing a role in causing cancer.

Some of these factors potentially increase the likelihood of a pet contracting cancer:


Some breeds of dogs are more likely to develop cancer than others. With cats, there isn’t as much of a connection between the cat’s breed and chances of contracting cancer, but Siamese cats get cancer at younger ages, and at higher rates, than other breeds of cats. Some dogs that have a higher chance of cancer are: Golden Retrievers, Boxers, Bernese Mountain Dogs, Rottweilers, Boston Terriers, Greyhounds, and Great Danes


Dogs that are large, or very large, seem to be more prone to developing bone cancer.


The likelihood of developing cancer increases as pets grow older. About half of older dogs will eventually wind up passing away due to cancer.*

Feline Leukemia Virus

Lymphoma, one of the most common forms of cancer in cats, is often caused by the Feline Leukemia Virus (FeLV) or Feline Immunodeficiency Virus (FIV).

Sun Exposure

Light colored cats and dogs, as well as pets that are known to be more prone to cancer, who are exposed to the sun are at a heightened risk for developing skin cancer.

Environmental Factors

Although the link is not definitively proven, there does seem to be a connection between oral cancer in cats and an exposure to secondhand smoke. As well, there are connections, as of yet not scientifically proven, between exposure to pesticides and herbicides and the development of cancer in cats and dogs. Consider that anything your pet is exposed to in the air may leave a residue on fur, which your pet licks and gnaws at daily, providing many opportunities for chemicals or cigarette residue to be ingested (or heavily exposed within a cat’s mouth, in the case of links between secondhand smoke and oral cancer).

Prevention of Cancer

Although some aspects of pets contracting cancer are a matter of chance and bad luck, there are some ways that responsible pet parents can help decrease the changes of their cat or dog getting cancer. Some preventative measure are:


While sometimes genetic causes will result in a pet getting mammary cancer even after being spayed, risks of mammary cancer are often reduced if pets are spayed before they go into heat for the first time. Even spaying pets after they have gone through heat can help to reduce the risk of cancer, so talk to your vet about the best time to spay your pet.


Though neutering does not protect against all prostate cancers, a neutered cat or dog will have drastically reduced chances of some cancers such as sertoli cell cancer, which usually only affects an animal's testicles.

Keeping Pets at a Healthy Weight

As well as all the other health risks associated with obesity, such as joint problems and diabetes, obesity is also linked to a higher risk of cancer. Aim to keep pets at a healthy weight, and exercise them frequently.

Vaccinating Your Pet

Some forms of cancer are associated with incidence of retroviruses like Feline Leukemia Virus. This virus is preventable with a vaccination, which is recommended for kittens. 

Limiting Exposure to Sun, Chemicals, and Smoke

Since sun, chemicals, and smoke can all potentially lead to an increased risk of cancer, it is helpful for pet owners to reduce the exposure cats and dogs have to these elements.

*Pet Cancer Awareness Foundation

More on Cancer in Pets

Managing Costs of Cancer Treatment for Dogs
Mast Cell Cancer
Histiocytosis in Cats and Dogs

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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