Our dogs, cats, and other pets can get cancer just like humans.  And, like humans, there can be different causes of cancer in animals.

The Merck Veterinary Manual has outlined the most common causes of cancer in pets, and what you can do to help lower the risk.


Some animals have an increased risk of certain types of hereditary cancer.  Some dog breeds can have a higher-than-average risk of cancer.  They include Golden Retrievers, Boxers, Bernese Mountain Dogs, and Rottweilers.

Researchers are studying the genes that are involved in pet cancers, as with the Golden Retriever Lifetime Study.

Environmental Factors

Carcinogens in a pet’s environment or diet can be another cause of cancer.  What are the known carcinogens that cause cancer in animals?

  • Ultraviolet radiation from sun exposure
  • Secondhand tobacco smoke
  • Herbicides, insecticides, pesticides
  • Air pollution
  • Substances like asbestos, radon, uranium, and vinyl chloride

You can eliminate many carcinogens in your pet’s home environment.  Never smoke around your pet and always look for pet-safe products for the home and garden.  Limit your pet’s sun exposure, especially if they have white fur.


Cancer is more likely to occur as your pet ages.  Experts suspect this may be due to a weakened immune system that cannot control mutated cells as well as it used to.  These mutations can lead to cancer.

Long-term exposure to carcinogens can also be a cause of cancer in older pets.


Some viruses can lead to cancer in animals.  Studies have found that infection with the feline leukemia virus leads to cancer in 30% of affected cats.

Dogs can suffer from a benign oral papilloma that is caused by a virus.  One genital cancer in dogs known as canine transmissible venereal tumor is also caused by viral infection.

Other Factors

The site of past injury or trauma can develop cancer, even after many years.  This can happen at the location of bone fractures and implants like pins, plates, and even microchips.

Cats have been found to develop sarcomas at old vaccination sites.  Rabies and feline leukemia vaccinations are usually implicated.   Indoor cats that are not exposed to other animals can benefit from a limited vaccination schedule.

For more information on pets and cancer, check out our blog article on how secondhand smoke can harm cats, dogs, and other pets (even fish!).



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