Updated October 14, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Most cancers in dogs don’t have a single identifiable cause. The biggest risk factors are age and genetics: some breeds, such as Golden Retrievers, Boxers, and Bernese Mountain Dogs, have much higher rates. Other known contributors include hormones (unspayed females have more mammary tumors), sun exposure for light-skinned dogs, and some environmental exposures. You can’t prevent all cancers, but some risks can be reduced.
Known risk factors
- Age: cancer risk rises sharply in older dogs.
- Breed and genetics: certain breeds are predisposed to specific cancers.
- Hormones: spaying before the first or second heat greatly reduces mammary tumor risk. Spay/neuter timing may affect some other cancer risks in certain large breeds, so discuss timing with your vet.
- Sun exposure: light-skinned, thin-coated dogs can develop sun-related skin cancers.
- Environmental exposures: studies have linked secondhand smoke and some lawn chemicals to certain cancers in dogs, though evidence varies.
- Chronic inflammation in some tissues.
Steps that may lower risk
- Discuss spay timing with your vet
- Keep your dog lean
- Avoid smoking around pets
- Limit exposure to lawn chemicals, and keep dogs off treated lawns until dry
- Use shade and pet-safe sun protection for light-skinned dogs
- Regular checkups and lump checks for early detection
Myths
- Routine vaccines causing cancer in dogs: not supported by evidence. (Injection-site tumors are a rare concern mainly in cats.)
- Kibble or grains causing cancer: no good evidence.
More: early signs of cancer in dogs.
Sources
- American Veterinary Medical Association (AVMA): Cancer in pets
- Merck Veterinary Manual: Neoplasia in dogs
- Glickman LT, et al. Herbicide exposure and the risk of transitional cell carcinoma of the urinary bladder in Scottish Terriers. JAVMA. 2004
- Hart BL, et al. Assisting decision-making on age of neutering for 35 breeds of dogs. Front Vet Sci. 2020
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.