Top 10 Warning Signs of Cancer in Dogs and Cats

May is Pet Cancer Awareness Month, a time to spread awareness of the symptoms of cancer in dogs and cats. As cancer is the leading cause of death in cats and dogs, knowing the symptoms your pets may present if they develop the disease can help you and your vet diagnose and treat your pet sooner. In order to help you protect your pet’s health, has pulled together the top 10 warning signs of cancer in dogs and cats.

1. Lumps and Bumps: Not every lump or bump is necessarily cancerous, but consulting with your vet is the only way to be sure. If the lump is growing or not resolving itself, contact your vet and he or she will do a biopsy to determine the contents of the bump.

2. Abnormal Odors: Foul odors from any of your cat or dog’s orifices and/or body parts may be a cause for concern. Cancers of the mouth, nose, or anal regions can cause your pet to emit offensive odors.

3. Abnormal Discharges: Discharges such as blood, pus, vomit, diarrhea, and any other abnormal substance being excreted from your pet’s body should be checked out by a veterinarian immediately. A bloated or distended stomach could also be a sign of internal discharge.

4. NonHealing Wounds: Lacerations or sores that do not heal within a normal time range on the surface of your cat or dog’s body may indicate infection, skin disease, and possibly cancer.

5. Weight Loss: Sudden weight loss in cats and dogs not on a diet can be an indicator of many diseases and illnesses. If coupled with another warning sign of cancer, you should contact your vet right away and inform him or her about your pet’s symptoms.

6. Change in Appetite: While a lack of appetite in dogs and cats can be an indicator of many things, they never stop eating without a cause. Not necessarily a sign of cancer, a decrease in appetite can indicate an oral tumor, which would make it painful and difficult for your pet to eat and swallow.

7. Coughing or Difficulty Breathing: Although symptoms of heart and lung disease, coughing and abnormal breathing can also indicate cancer. This symptom will most likely occur if the cancer in your pet’s body has metastasized into his or her lungs.

8. Lethargy and Depression: If your pet has cancer, there is a chance that he or she will suffer from depression and sleep more, become less playful, and be less willing to go for walks. Although lethargy or depression in dogs and cats can set in with any illness, it is commonly seen in pets that have cancer.

9. Changes in Bathroom Habits: Any changes in your pet’s bathroom habits including difficulty using the bathroom, frequent bathroom use, and blood in urine or stools are potential warning signs that cancer has developed in your pet.

10. Evidence of Pain: Limping or other evidence of your dog or cat in pain when he or she is active, or if the pain is too great for them to be active, can be indications of cancer of the bone.

While no one sign purely indicates cancer, a cat or dog displaying two or more of these symptoms should be taken to the veterinarian for an exam so that he or she can be properly diagnosed and treated accordingly, because early detection can make all of the difference in the case of a positive diagnosis.


  1. Mina says on  05/21/2012 at 4:05 pm

    This is great for people to know, but the one thing I don’t see he is Hair loss. I lost my beagle to Lymphoma and hair loss was the only sign we had.

  2. Charlotte says on  05/21/2012 at 4:11 pm

    What kind of hair loss Mina? Patchy? All over? My dog has had hair loss due to staph infections in his later years.

  3. Mark says on  05/21/2012 at 4:11 pm

    Hombre and me are fighting together to defeat his bone cancer. We already knocked his liposarcoma into submission.

  4. Kirsten says on  05/21/2012 at 4:14 pm

    You also need to know if your breed, and mixed breeds can be susceptible to the pure breeds, are more likely to develop. For instance GSD, from what I was told by my vet in Massachusetts, are likely to develop spleen cancer, which is what killed my last dog. He showed signs of being sick, took him in, we did a general exam, needle biopsy of a lump, and he was dead before the results were in. He was ill for maybe 2 weeks.

    • mary says on  07/25/2013 at 7:53 pm

      Kirsten I just lost my baby 4 months ago he was with me for9years and 7 month he got bloted I call his vet they not wouldn’t check him out they wanted 300 dollars first I ask they if I could pay per month they wouldn’t see him they let my baby die I call them and told them they lost me as their customer because they let my baby die he was their patient and wouldn’t save him they let him die I know you send this message last year on may21 2012 but I didn’t have a computer the I hope you see this message message I wrote you he passed away 3 18 2013 he was born 8 8 2003 I buried him in my backyard with his blanket wrap around I put a little white fence around his grave with white rocks on top also a white cross that tells his name when he was born he has little angle a dog flowers in a vase ,plastic ones everything I put there with clear bags over them so that the sun won’t get to faded and keep the rain off of them I hope I get a answer back soon Mary

  5. Our GSD died of spleen cancer as well. He was gone within a week. Although, the cancer had not spread from his spleen, he was 12 and didn’t wake up after the surgery.

  6. Gina says on  05/21/2012 at 4:22 pm

    We found our dogs thyroid cancer while scratching his neck. Took him to the vet. This is a great article. Thank you

  7. My old lab has some of these symptoms, made an appointment for him for this Saturday. Hope all goes well as I adore my baby.

  8. My friend lost both her gsds to spleen cancer and my old (only 10) lab bitch had a cough within 3 weeks she had lost 5kg and I didn’t wake her up from her exploratory op … Millie I miss ya girl xxx

  9. I have to have a Mast Cell Tumor removed on Friday by a specialist surgeon cause it’s so close to my tail and they have to create a little flap. It’s only the size of a pea but a 3 cm radius has to be taken to hopefully get a clear margin. Mum checks me over all the time, just to be sure. I am going to be fine but mum and dad love be so very much they’re worried sick. Great article…thank you!! 😀

  10. Good luck Dexter x

  11. Lalana says on  05/21/2012 at 4:51 pm

    Cancer sucks no matter if you have two legs or four!

  12. Allison says on  05/21/2012 at 4:55 pm

    My Brodie GSP was diagnosed right @ 3 years ago. Vet said he would make it 6 months. I cherish every day with him.

    • mary says on  07/25/2013 at 8:08 pm

      you are right its not us their owners its the vets because they all the time want a lot of money off the animals should have a vet that will take their needs free that loves animals and wants to help low income and poor people that don’t get very much money from mary

    • Anonymous says on  01/06/2014 at 2:15 am

      I am sry to hear about ur dog .. I love dogs n I knw bout that felling after reading this I got tears In my eyeys:-[ :(:(:(:(

  13. Ummm no actually its not the leading cause of death. Its idiot humans that are the number one cause of death.

  14. Thanks for the information!

  15. My boy Biscuit (Chinese Shar Pei) had Mast Cell Cancer appx 2.5 years ago and had a tumor removed by surgery. We’ve been treating him with K9 Immunity ever since and I believe it has helped him remain cancer free… They will work with your Vet for the best possible outcome…

  16. HBobbie says on  05/21/2012 at 5:21 pm

    Thank you for posting this information for us furbaby Moms

  17. Christine says on  05/21/2012 at 5:27 pm

    Very valuable info! Will always keep in mind! Thank you!

  18. Jen says on  05/21/2012 at 5:59 pm

    The only one my Beau Beau had was lumps. It was lymphoma. :(

  19. Marion says on  05/21/2012 at 6:42 pm

    My dog is a blood donor and gets a complete blood, fecal and urine work up once a year for free
    Its a great little perk
    If you aren’t sure you can afford the tests on your own why not look into blood donation in your area?
    Donation is quick and not any harder on the dog than it is on you – my Ruby bounces back in a day or two and she gets to save lives!

  20. Hugs^^^Orion crossed from it 2 yrs. ago Weds….

  21. Tammy says on  05/21/2012 at 10:39 pm

    Pib has 6 of the 10.

  22. Praying for you and your family Dexter !

  23. Ramona says on  05/22/2012 at 2:36 pm

    Sadly not any of these were evident with my Sarge. He was diagnosed with epilepsy at age 1 1/2. We now assume that the seizures were caused by brain cancer. Sargie passed shortly after his 4th birthday. He went into a seizure and didn’t come out. He was full of life, ate like a fiend, playful, fun and a wonderful baby. He had no tumors or patches or odd colour skin. The only indication of something was the seizures. We did treat the seizures with medication and for a year and a half to two years he was seizure free. Cancer never even entered into our heads or the Vets.

  24. Anonymous says on  12/10/2012 at 2:12 pm

    My Golden Retriever “Samson” just got diagnosed with cancer in the lymph nodes. He’s 10 and I’d like to have him around longer but I’m struggling on what’s the best thing for him is right now…

  25. Ashley says on  10/13/2013 at 12:50 am

    Our German Shepard lab mix has all of a sudden in the past couple of weeks developed a big bump on his back right leg. I am hoping its not something too serious cause I can not afford a vet visit or bill.

  26. Candy says on  12/21/2013 at 1:56 am

    I think my dog has cancer. She is very old and has a few symptoms. Can’t afford a vet bill.

  27. Connie Gallegos says on  06/05/2014 at 8:48 pm

    I gotta question for those of u who r dog lovers. I have a husky he sheds every summer. Lately he hasn’t been eating very much. I can tell he has lost weight. He sleeps a lot but whenever we take him outside he runs round and goes crazy. I’m just worried cuz he doesn’t eat like he use to and he looks sad. The only symptoms I see, don’t eat much, loss weight n sleeps all day and runs round all night

    • Anonymous says on  03/06/2015 at 12:31 pm

      If you can’t affor to take your pets to the vet I’m sorry to say then you shouldn’t have them. It isn’t fair to them. It you can’t take them to a vet or feed them or whatever needs to be done. We have 3 dogs and no children. They are taken care of as if they are our kids.

      • Some people don’t have much, but a pet might give them something to love and cherish, or the companionship they need. Some people might be desperately lonely, depressed or be experiencing other problems in their lives. In some countries there are animal charities that may help. Some ask for a donation or provide much cheaper alternatives to regular vet’s bills for those who may have lost a job, are disabled, or for other reasons have a low income. (These charities don’t moralise, but some may ask for proof of income) Incidentally, vet’s bills may be far too high when organisation exist like Animal trust (UK) My dog has to have Xrays later today which will hopefully allow for treatment that might help prolong his life. I can afford the £105 for these, whereas just under £500 quoted by Gyp’s previous vet might have felt a bit over the top in comparison. My reply at 4:50am when my dog’s appointment is not until 1:50pm might be some indication of how some of us feel when our dogs may gratefully feast on scraps of food in necessary, but ultimately loved til the end. The tears can go on for many years, but there is someone greater than ourselves who sees them.

  28. Anonymous says on  06/23/2014 at 2:52 pm

    My dog has like half of these, very worried.

  29. Shirley Rowarth says on  05/26/2015 at 3:17 am

    Please don’t moralise with people who are heartbroken/worried sick about a pet they love while not having much money. Maybe their pet gives them immense comfort when they don’t have much else to hope in at present. They’re company and are deeply loved. Losing them is one of the hardest things to bear and the tears that can flow for many years are hard enough to cope with. Animal charities exist in some countries for those who can’t afford regular vet’s bills. They may depend on donations or provide much cheaper alternatives. Some may require proof of income if on benefits/state aid (due to a job loss perhaps? Nobody judges there anyway) Humanity, please! Pets are grateful creatures who may feast on scraps of food if necessary. They’re loved and lovable…as are the people who love them to the end.

  30. Andrea says on  06/24/2015 at 5:20 pm

    My gorgeous wolf dog got cancer he was 12years old. We did not know at first that he had it as he was stiĺl acting like a puppy most days. He started limping on all fours and his breath was smelling badly, we thought it was just old age. He started being extremely tired and not himself. He was moulting a lot and I noticed 3 lumps under his fur. when he stopped eating his favourite things and drinking more water I took him to the vet’s. Thinking he would be ok little did I know. The vet checked him over and said he had aggressive cancer and had to put him to sleep. The thought of losing my best friend was unbearable but the vet said treatment would not work. I miss him every day but knowing he is not in any pain was the kindest thing to do.

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