10 Warning Signs of Cancer

If your dog exhibits any of these symptoms, schedule a vet visit.


In dogs, just like in people, cancer doesn’t tend to markedly affect life out of the blue. More frequently, signs of the disease progress gradually. As we discussed in the April issue, there’s good news in that researchers are working on being able to detect cancer in the blood as early as possible to initiate treatment before the disease has had a chance to progress. But they’re not there yet. In the meantime, the Veterinary Cancer Society has identified 10 common warning signs that a dog may have cancer and should be taken to the veterinarian for further testing.

None of these signs is cause for panic. They are not specific to cancer and could also indicate other illnesses that are not at all life-threatening. For example, difficulty eating could simply be a sign of a painful tooth that makes it difficult to chew. Sores that don’t heal could indicate that your dog’s immune system is reacting to allergens.

That said, if a problem lasts at least a week or two and shows no signs of abating (even if it’s not on the accompanying list), a professional examination is in order. It’s much better to go through the trouble — and worry — of getting your dog to the vet for a work-up than wait because you fear the result. You don’t want to run the risk of getting a cancer diagnosis that’s too late to treat effectively.

The tests to check for cancer will vary depending on the signs the dog presents with. Sometimes just palpating (feeling) the dog along certain spots on his body will provide a clue. But not all cancers present as a bump or lump. For that reason, a vet will often get imaging in the form of x-rays, ultrasound, CT scans, or MRI.

None of these imaging tests is definitive for cancer, either. A mass viewed during an ultrasound, for example, could indicate a number of abnormalities that are not in the least cancerous. But imaging tests can be highly suggestive, especially if they show that the mass has invaded nearby body tissue. That in turn can lead to a biopsy, which is the gold standard for cancer detection.

10 Possible Signs of Canine Cancer*
  1. Abnormal swellings that persist or continue to grow
  2. Sores that don’t heal
  3. Unexpected weight loss
  4. Loss of appetite
  5. Bleeding or discharge from any body opening
  6. Offensive odor
  7. Difficulty eating or swallowing
  8. Hesitation to exercise or loss of stamina
  9. Persistent lameness or stiffness
  10. Difficulty breathing, urinating, or defecating

* While the Veterinary Cancer Society has named these possible signs of cancer, the Animal Cancer Foundation also lists swollen lymph nodes, abdominal distention, and chronic vomiting or diarrhea.



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