Updated October 13, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Cancer is one of the leading causes of death in older dogs, and catching it early gives more treatment options. Early warning signs include new or growing lumps, sores that don’t heal, unexplained weight loss, loss of appetite, lasting lameness, bleeding or discharge, unusual odors, and trouble eating, breathing, urinating, or defecating. None of these signs means cancer for certain, but each is worth a vet visit.
Warning signs to watch for
- A lump or bump that appears, grows, or changes
- A sore that doesn’t heal
- Unexplained weight loss
- Loss of appetite
- Bleeding or discharge from the mouth, nose, or other openings
- A bad smell, especially from the mouth
- Difficulty eating or swallowing
- Tiring easily or reluctance to exercise
- Lameness or stiffness that lasts
- Difficulty breathing, urinating, or defecating
- Swollen lymph nodes (under the jaw, in front of the shoulders, behind the knees)
Lumps: see something, do something
The Veterinary Cancer Society recommends having any lump checked with a needle test if it’s the size of a pea or larger and has been present for a month. Many lumps are harmless, but you can’t tell by feel. See what to expect from a fine needle aspirate.
Screening for older dogs
- Checkups every 6 months for senior dogs
- Monthly at-home “nose to tail” checks for lumps
- Bloodwork and urine tests as your vet recommends
- Imaging if signs suggest internal disease
Higher-risk breeds
Golden Retrievers, Boxers, Bernese Mountain Dogs, Rottweilers, Flat-Coated Retrievers, and several other breeds have higher cancer rates, so regular checks are especially important.
More: cancer symptoms in dogs.
Sources
- Biller B, et al. 2016 AAHA Oncology Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2016
- Veterinary Cancer Society: Warning signs of cancer in pets
- American Veterinary Medical Association (AVMA): Cancer in pets
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.