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Top Ten Signs of Cancer in Pets

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Cancer is the #1 Disease-Related Killer of Pets

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. According to Dr. Lorie Huston, she 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.

#10 Lumps and Bumps

Not all lumps and bumps on or under your dog or cat’s skin will be cancerous, but there is no way to know for sure without getting your veterinarian involved – 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.

#9 Abnormal Odors

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

#8 Abnormal Discharges

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

#7 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.

#6 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.

#5 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.

#4 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.

#3 Lethargy or Depression

If you notice your pet is not acting like itself – sleeping more, less playful, less willing to go on walks or to exercise – 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.

#2 Changes in Bathroom Habits

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

#1 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).


Please see the next slide for more.

Learn More

The AVMA's Cancer in Animals brochure has more information and links on cancer in pets, as well as guidelines for veterinary hospice care.


We also have our own in-house veterinary oncologist, Dr. Joanne Intile, DVM, DACVIM, who has a regular Daily Vet blog. You can read more of her blog posts here at Dr. Joanne Intile's Archives


Related Articles

Is a Cancer Specialist Necessary for Your Pet?

What Causes Cancer in Pets?

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Comments  9

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  • Tumor in dog
    08/20/2014 04:24pm

    My dog has a lump on his belly, near his penis, that he kept licking. I took him to two different vets and neither said they could see the lump. I could not understand that since the lump was very obvious. Forward 1 1/2 years.....the lump is now huge and the dog is not eating well at all. Took him back to one of the previous vets and he says it could be cancer. The tumor does not seem to be painful. He said since the dog is old (80 pounds and about 12 years old) just take him home and let him live out his last days. The tumor is huge and still growing. I am concerned about pain and the possibility of obstructing urine flow. I can't afford to go back to the vet or have surgery on our rescue dog. How should I handle his care? When is it time to have him put to sleep?

  • 08/22/2014 01:35pm

    Dear Skizzatt:
    So sorry about your dog. He could have had a biopsy when you first noticed the lump and had it removed then before it was too late. Sometimes I think some vets just don't want to be bothered with what they think is not worth their time to look into it or they are just too busy. I would certainly go back to those doctors and let them know if they had just spent a little more time or brought him back in a few months to check him again, you might still have him with you today.

  • 08/25/2014 12:39am

    Dear skizzatt,
    There is financial assistance with vet bills, you just have to know where to look.
    Here is one, Canine Cancer Awareness page
    [email protected]
    If they can't help ask who can.

  • 11/04/2014 06:56pm

    Is this available in Australia ???or is this from the states ??

  • 10/02/2014 10:47am

    Hi Skizzatt,
    I have 2 dogs and 1 cat. I have used in the pass a natural product called Inositol Hexaphosphate (IP6) and it reduced my dogs tumor to nothing. The vet had given him 2 months to live. It took about 1-2 weeks to take effect and after 6 months we brought him back for an exam and the vet tumor was gone. He lived a healthy life for another 2 years (he was 14 years old when he passed away). I am again using this product for my dog who is 10 years old as she has a tumor under her ear. I just started yesterday with this. It is worth a try, you can purchase at a health food store. I hope this could help you with your dog. Good luck.

  • 11/04/2014 07:08pm

    Hi I'm very interested in this medication for my dog ,he is only 5years old he doesn't seem sick??? But we noticed a lump on his chest .. They took It out sent it to pathology it came back high grade .. The vet said life expectancy 3-6weeks I'm in shock!!!!! He looks to healthy ???? I would like to try this treatment ...where can I get it please !!!how much does it cost ??? I'm a pensioner I don't have a lot of money ...

  • 11/05/2014 11:38am

    Hi Izzy,
    Sorry to hear about your dog. You may purchase this product at a Health food store. I'm in Canada are you in the UK? I found a site with a mini protocol for dog cancer, my vet called yesterday, we had a biopsy done and she has stage 2 of lymphoma cancer, she has 2 months. I'm not giving up. She is still in very good spirits, IP6, with Q10 and I'm starting another product today called colloidal silver. Here a site I found.

  • 12/12/2014 11:48pm

    Go to a more responsible Vet. Usually if the lump is hard, it most likely is cancer. They should have done a biopsy, they could have taken right out. Run to a vet and demand a biopsy. If it bleeds after the needle is out, then it sure is cancer. It could also be pre-cancerous. I wish you the best of luck. Next time a Vet brushes you off, brush them off, for good.

  • natural medication
    09/17/2014 11:13am

    Dear friends
    I want to tell you about a natural medicine used by the natives of the Amazon to cure diseases.
    today many people are cured of cancer, my theory is if heals people because I do not try to diseases of our pets.
    more information to my email:
    [email protected]