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Top 10 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?


Comments  27

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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.

  • 01/23/2015 04:05pm

    Hello Monic
    Could you please tell me the weight of your dog and the dosage you were giving it?
    Thanking you

  • 01/23/2015 08:38pm

    Hi Subomann,
    My dog Mya was 85lbs, she passed away 3 days ago on January 20th, 2015. Her lymphoma cancer took over. We did everything we possibly could for her, but unfortunately the cancer came back with a vengeance. The IP6 did not work for this cancer, we've been fighting since the fall with the IP6, Q10, colloidal silver, vitamins C and E, selenium, alka base, sanuvis, in the end we had to give her the Prednisone. Approx. 10 years ago we had a Doberman mix that had a big tumor on his chest, the IP6 shrunk this tumor and he lived for an additional 2 years. I guess the IP6 works only on certain cancers. Our vet said that lymphoma is a terminal cancer. We paid big bucks to see a natural path veterinarian (our regular vet was open to this). Mya lost her best friend Sally on July 12, 2014 to bladder cancer, by September Mya got cancer, both these dogs were boxer mixed and they both lived to almost 10 years old.

  • 01/24/2015 04:27am

    Thank you for your reply Monic. I am sooo sorry to hear of your loss 2 in 6 months you must be devastate. At least the two of them are together now.
    All the best

  • 01/23/2015 08:44pm

    Sorry subomann, I didn't give you the dosage. I have lots of info, if your dog has a different cancer than lymphoma it would be worth trying. Protecting their immune system with Q10 (200mg) and colloidal silver is extremely valuable. IP6 dosage was 3 capsules in morning and 3 capsules at night. Leave me your e-mail address and I will be happy to share all the information we have.

  • 01/24/2015 04:28am

    Thanks Monic my e-mail is [email protected]

  • 10/19/2016 07:39pm

    HI Izzy, I hope you and your furry friends are all healthy and happy. I got some inconclusive news the other day but the Vet said his gut feeling is its bladder cancer. I read what you gave him but I am curious was their a brand better than another? I found the mini protocol from this site and truly appreciate it!!!! I just need to find an effective supplements to give him. I realize these posts are pretty old but hoping someone might see this and respond. Thanks.


  • 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.

  • 01/28/2015 02:34pm

    Can you tell me the dosage for the IP6. I want to start her on it right away. She weighs 23 lbs and was diagnosed with cancer yesterday. Thank you for your help

  • 01/28/2015 02:41pm

    Does IP6 work on lymphoma? I read in other threads it did, but now I read this thread and Subomann said it didn't work? I'm confused?

  • 01/28/2015 04:04pm

    Hi Marilee
    I am sorry I can't answer this for you. It wasn't me that said it didn't work.

  • 01/28/2015 07:23pm

    Hi Marilee,
    Unfortunately lymphoma is a terminal cancer. I searched everywhere on the Internet and did not find anything on a cure for lymphoma cancer. IP6 has worked in the pass for 1 of our dogs, but it was a mass cell tumor cancer NOT LYMPHOMA. Hope things work for you in your fight with the cancer. Our dog was comfortable up into the end. The IP6 is now called Phyto-C but it has the IP6 500mg along with Vitamin C which is good for cancer treatment.

  • 01/28/2015 07:31pm

    Here is a site on mini protocol for cancer. It may help you. My dog was 85lbs and she was getting 3 capsules in morning and 3 at night along with the Q10, colloidal silver etc... She was on a bunch of natural stuff until the end when we put her on prednisone. We are now helping a rescue dog to help heel the broken heart, it's the hardest thing in the world to go through when your dog has cancer. All the best to you.


  • 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]

  • Our faithful dog KoKo
    09/04/2015 04:12pm

    My wife & I have a female King Charles Cavalier, a beautiful dog. We were told last week that she has lymphoma & there is nothing that can be done. Our dog is only six years old and just last month she seemed to be as healthy as any other dog, but about three weeks ago, we notice she was not her usual self. She wanted to be by herself, would not eat, became very lethargic and she has bad diarrhea. We have scheduled to have her put down tomorrow because it seems like she is in a great deal of pain. This is more than a cry for help, because we love our dog & want to do what is right for her, she has been so good to us. Thank you for listening.

  • Koko
    10/03/2015 08:35pm

    Hi. I was so so sad to read about KOKO. A life cut short to early. So sorry for your loss.

  • Cuddly kitty has cancer
    03/31/2016 12:50pm

    I have a sick kitty with a form of cancer called Angiosarcoma. He just turned 6 in March, and my family and I love him so much. His name is Cuddley, and he is super cuddly so the name fits. He was 21 pounds before being diagnosed, and now is down to 15 pounds. He is very long and is naturally a large cat. His brother passed away last year with an unrelated issue, and it would be very hard for our family to go through that again. My son and daughter both love their kitties; they have helped them both throw some very difficult times in their lives.
    I have started a go fund for Cuddley. We never got to do this for his brother, and I regret it. I don't want to wait until it is to late for him, so I am trying to help him fight this battle.

    If anyone reads this, can you please share my link below, to help get cuddley's story out there. Thank you so much,

  • 03/31/2016 12:54pm


  • Weight loss
    04/09/2016 11:35am

    My cat Bootsie is 15 yrs. old and is losing a lot of weight,he also vomits frequently but still has a large appetite.I even have to watch while my 3 cats eat so he doesn't take food from my other 2 cats.I`m concerned about his weight loss.He also howls after using litter box at times.

  • 04/15/2016 05:16pm

    What type of cat food have you been feeding him? The high appetite could be a result of hyperthyroidism, and vomiting could be kidney disease, caused by hyperthyroidisim, or he could simply be allergic to some ingredients in his food. You should get him tested at a vet to be sure. If he keeps vomiting, he will continue losing more weight, which will cause dehydration, among other issues, and be life-threatening.

    Since he's thin already and possibly diabetic and constipated (due to the howling after using the litter box), you should try feeding him lower carb, wet canned food. With dry food only, he likely isn't getting enough water, which will further dehydrate him. You can try the Friskies Pate flavors, like Poultry Platter and Mixed Grill. They are free of likely allergens, such as soy, corn, wheat, and fish. Some of the classic Fancy Feast flavors should be okay, too. If he was simply allergic to one of those ingredients, his vomiting may stop with a simple diet change. If you're up to it, you may also want to consider researching homemade diets for cats, but you need to be careful to include all the nutrients cats need.

  • Bowel cancer in dogs
    05/12/2016 07:44am

    I am absolutely beside myself as I have just lost my 12 year old Westie, Millie after many visits to the vet. He was dismissive of her symptoms yet I was extremely concerned that it was more serious after being given a diagnosis of IBS. I asked for x-rays and blood tests which weren't carried out. She was bleeding from her rectum for many months, losing weight and had a prolapsed rectum. I beg the question had she been treated earlier would she still be alive ? It was a different vet within the same practice that spotted the tumour too late. Heart broken. Maybe a cautionary tale for other dog owners. I wanted to get a second opinion. I am wracked with guilt that I trusted the vet and didn't go elsewhere.