Top 10 Signs of Cancer in Dogs and Cats

Many people do not realize that cancer is not just a human condition — it affects our pets as well. In fact, cancer is the number one disease-related killer of dogs and cats.† Dr. Lorie Huston tells her clients to be on the lookout for the following signs. While these symptoms are not purely indicative of cancer, if a pet begins to exhibit them you should visit your veterinarian immediately. Just like with people, the earlier cancer is caught the better.

1. Lumps and Bumps

Not all lumps and bumps on or under your dog or catís skin will be cancerous, but there is no way to know for sure without getting your veterinarian involved Ė this is especially important if the lump is not resolving itself or is growing in size. A needle biopsy is commonly done and a veterinary pathologist can let you know if the cells are cancerous or not.

2. Abnormal Odors

Offensive odors from your dog or catís mouth, ears, or any other part of your petís body, should be checked out. Oftentimes cancers of the mouth, nose, or anal regions can cause such foul odors.

3. Abnormal Discharges

Blood, pus, vomiting, diarrhea, or any other abnormal substance being discharged from any part of your petís body should be checked out by your veterinarian. In addition to that, if your dog or catís abdomen becomes bloated or distended it could be a sign of an accumulation of abnormal discharge within the body.

4. Non-Healing Wounds

If your pet has wounds or sores that are not healing, it could be a sign of infection, skin disease, or even cancer.

5. Weight Loss

Cancer is among the list of diseases that can cause weight loss in a pet. If you notice sudden weight loss in your dog or cat (and it is not currently on a diet), along with other signs from this list, be sure to mention it to your veterinarian.

6. Change in Appetite

Dogs and cats do not stop eating without a cause. While a lack of appetite does not automatically indicate cancer, it is still something to be discussed with your veterinarian. Oral tumors can also cause difficulty or pain when eating or swallowing.

7. Coughing or Difficulty Breathing

Coughing or abnormal breathing can be caused by heart disease, lung disease, and also cancer. Cancer can metastasize through the lungs and cause these symptoms.

See Also: Dog Food Allergy Myths

8. Lethargy or Depression

If you notice your pet is not acting like itself Ė sleeping more, less playful, less willing to go on walks or to exercise Ė this can also be a sign of cancer. Once again, lethargy or depression is not a symptom confined to cancer, but an accumulation of any of these signs is reason enough to speak with your veterinarian.

9. Changes in Bathroom Habits

Changes in your petís urinary or bowel habits Ė difficulty using the bathroom, frequent bathroom use, blood in urine or stool Ė these are all potential signs of cancer.

10. Evidence of Pain

Limping or other evidence of pain while the pet is walking, running, or jumping is mostly associated with arthritic issues or joint or muscle diseases, but it can also be a sign of cancer (especially cancer of the bone).

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Top 10 Signs of Cancer in Pets originally appeared on


Marie W
Marie W1 years ago

Thanks for sharing.

Melania P
Melania P1 years ago

Good list, thank you. Sharing as well!

Joy T
Joy T2 years ago

Good to know!

heather g
heather g2 years ago

What a sad-looking picture of a sick dog.....

PlsNoMessage se
PlsNoMessage se2 years ago


Leo C
Leo C2 years ago

Thank you for sharing!

iskrica k
iskrica knezevic2 years ago

thank you!

Ann B
Ann B2 years ago


Marianne R
Marianne R2 years ago

Thank you

Marianne R
Marianne R2 years ago

Very informative. Thank you