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10 Early Warning Signs of Cancer in Your Dog or Cat

Different symptoms can indicate a variety of illnesses in pets, but it’s important to be on the lookout for these red flags.

By: raneko
Cats and dogs get different types of cancer. By: raneko

It’s never a topic any of us like thinking about — the big “C,” cancer. Most of us have probably been touched by it in some way or another in our lives.

Whether we have been diagnosed with it ourselves or a family member or friend has, cancer is never an easy diagnosis to hear or bear. It means worry, fear, pain and uncertainty.

What many people don’t realize is that pets, like people, can get cancer too, and that it is actually pretty common. As with people, in pets there are varying degrees and progressions of cancer, so I think it’s important to know some of the signs to watch out for.


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Early discovery with most cancers goes a very long way toward a successful recovery.

1. Suspicious Lumps or Bumps

We hear a lot about women giving themselves regular breast exams and checks, but you never really hear about checking your pet. When you’re engaged in playtime or just patting time, run your hands over your pet just to get the lay of the land.

If you encounter a lump that you haven’t felt or seen before, it’s probably not a bad idea to get it checked out. Chances are it’s nothing — but as they say, better safe than sorry.

2. Strange, Off-putting Odors

Every once in a while your dog is going to let out some gas, sure, and it is never pleasant. But if you notice a persistent odor around the mouth, ears or anal areas, it is time to get that checked out. Some cancers do cause foul odors.

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3. Unexplained Discharge

Pus, blood or anything out of the ordinary should be looked into immediately. After all, blood comes from somewhere and if you can’t see where your pet is bleeding from, there may be internal bleeding.

Pus can signify an infection or may be a sign of something more serious.

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4. Persistent Wounds

This could be a sign of an infection or skin disease, but it could also be cancer. Most superficial wounds heal within a week or so, but if your dog or cat has a wound that just isn’t healing, get it checked out.

5. Unexplained Weight Changes

Sometimes your pet is just pudgy and you have to put her on a diet. It happens to a lot of us, but if your pet is losing weight and you haven’t changed the diet, that is something to look into.

Many cancers can cause dramatic weight loss in both people and pets.

6. Appetite Changes

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Feeling ill can put many pets off food, but a persistent disinterest in feeding time is something to ask your vet about. Another thing to watch for is increased thirst.

7. Coughing or Difficulty Breathing

As with the other signs on this list, it’s difficult to point at a symptom and say, “That’s cancer!” with absolute certainty. Many things can cause coughing and/or breathing problems. Colds, kennel cough and aspiration pneumonia are just a few illnesses that can cause this symptom.

However, some lung cancers and tumors can manifest in these symptoms. Difficult respiration should always be cause for concern.

8. Sudden Lethargy or Depression

Pets have feelings, and if they seem downcast day after day there may be something going on inside them that you can’t see. If they have cancer, a great deal of energy is being devoted inside to fighting the disease, and it can cause your pet to seem tired and not interested in doing much more than lying down or sleeping.

9. Unexplained and Persistent Changes in Bathroom Habits

A house-trained pet losing bowel or bladder control occasionally is somewhat common. Being inside too long, drinking too much water, a getting stomach bug could be causes.

Persistently losing control is another matter. Constant and persistent diarrhea or constipation is a sign of ill health as well. Every animal eats something that doesn’t agree with them in their lifetime, of course, but when bowel or bladder control is lost or sudden stool or urine changes happen with no explanation, that’s definitely worth a mention to the vet.

10. Unexplained Pain

If your pet is limping, showing sensitivity toward a certain area of the body or snapping at you when you go near, your pet may be in pain.

If your pet has pain and you can’t explain it, get it checked out by your vet just to be safe. The hardest thing about diagnosing cancer is that it manifests in symptoms that are so broad and across the spectrum.

You know your pet better than anyone else. Watch for obvious changes. Don’t be afraid to call your veterinarian and ask for advice, a quick opinion or for your pet to be seen.


This pet health content was reviewed by a veterinarian.

Melissa Smith

View posts by Melissa Smith
Melissa Smith, discussions manager for Petful, has been researching and writing about pet behaviors for several years. A longtime pet lover, she lives in Massachusetts with her teenage son, their cat Harrison and the spirit of their German shepherd named Gypsy. Melissa is pursuing a bachelor’s degree in multimedia design and hopes to adopt as many needy animals as she can.

Don’t Miss: See why Dave from Petful thinks The Farmer’s Dog is the best new dog food in the U.S. for a happier, healthier dog: Here is his review. For cats and multi-pet households, Dave’s top pick is NomNomNow. See why here.

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