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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Signs of Dog Cancer and Decompensation

Updated: November 22nd, 2018

People are often stunned to find out their dog has cancer. Why? Because cancer seems to hit out of the blue. I often hear “but he’s been fine until the last couple days!” In this article, I’m going to take just a minute to explain why “cancer” seems to happen overnight. (Hint: it’s because of dog cancer decompensation … not cancer itself.)

“Signs of Dog Cancer” Are Really “Signs of Dog Cancer Decompensation”

Search for the warning signs of dog cancer, and you’ll find plenty of listicles that include items like the following:

  • a new lump that is hard
  • a limp
  • coughing
  • weight loss
  • loss of appetite
  • vomiting
  • diarrhea
  • thirst changes
  • bad breath
  • yellowing of the skin or eyes
  • abdominal swell
  • difficulty breathing
  • spontaneous bleeding
  • unusual odors

But those are not signs of cancer. They are signs of dog cancer decompensation.

Your dog has had cancer for a lot longer than you realize. The signs listed above are actually signs that your dog’s body has stopped being able to compensate for cancer, and her body’s normal functions are breaking down.

Looking back at your dog’s last few months, or even year, you might think I’m crazy.

How is it possible that a dog can act totally happy, eat, drink, move around, socialize … and have cancer?

Don’t sick dogs act sick? Well, let’s take a look at that.

Decompensation Defined

The clearest definition of decompensation I’ve found is this:

“Decompensation is the functional deterioration of a previously working structure or system.”

Every organ and system in the body function well under normal circumstances. And every organ is designed to have lots of built-in safety systems so that if something goes wrong, the organ can STILL function while it repairs itself.

So, when a medical problem is introduced, the body can “compensate” for it. Let’s take a non-cancer example.

Say you are using a hammer and hit your thumb. That’s our medical problem: your bruised thumb.

The tissues immediately swell up. That’s the immune system sending fluid to the area both to keep it from moving too much (which could further injure it), and also to bring white blood cells to the area to start helping repair the damage.

Your immune system is “compensating” for the medical problem by sending help.

Now, normally, your thumb would heal in a few days or a week. You might not even really notice the thumb’s hurt, after a while.

But let’s say that you damaged your nail very badly in the strike. The body simply can’t repair the damage done. After a week or so, you might find your nail falling off. Now it takes months for your nail to grow back in.

Well, that’s your “decompensation,” right there. Normally, you have a nail on your thumb. But now, you don’t. Your body could not compensate for all the damage done.

So now you’ve got a clear sign … for months … that you have been damaged, and that things aren’t normal.

When Safety Systems Fail

When your dog has cancer, her body will kick in all sorts of safety mechanisms (depending upon where the tumor is) to keep the body working properly. Dogs act normally during this time.

So do people, if you think about it. You probably know someone who has had cancer. Did they feel terrible right at the beginning? No … we don’t start really noticing symptoms until cancer has disrupted our health. Until our safety systems start failing.

So what we see listed as the “signs of cancer” are not really signs of cancer at all. They are signs that cancer has gone past a certain tipping point.

They are signs of dog cancer decompensation.

They are signs that cancer is in a late stage.

In other words, once a dog starts to act sick, it’s already late in the game.

What to Do If Your Dog is in Decompensation

If your chest is tightening as you realize that your dog isn’t “suddenly sick,” but may have had cancer for a while, please take a few deep breaths.

This is a difficult concept to accept, and it’s totally normal to feel, well, to feel awful about it. Just because we usually find cancer late (after decompensation) doesn’t mean that we can’t do anything about it. There are lots of things to do to help your dog’s life quality and even optimize longevity.

So if you haven’t had a diagnosis yet, get one. Knowing what you’re dealing with will help you to make decisions. And if you do know it’s cancer, don’t be afraid to get a second opinion, just to make sure. Any professional vet will be okay with this, and it wise to double check to make sure the dog cancer journey is a path you are on.

Get the Dog Cancer Survival Guide to read more on End of Life and Hospice Care, in Chapter 25

Bottom Line: Test Healthy Dogs for Cancer

The fact is that one out of two dogs over ten gets cancer, and one out of three overall get cancer. It’s the number one killer of dogs at this point. So we should all be taking it very seriously, and testing dogs for cancer, earlier, when they seem healthy.

Starting in the last quarter of life at the earliest, get annual (or more frequent) imaging done to look at internal organs: X-rays, ultrasounds, etc. Don’t ignore lumps and bumps, but get fine needle aspirates, biopsies. Blood and urine tests can serve as critical screening tools.

When’s the last quarter of life? There’s a comprehensive list in my book for breeds and their average life expectancy, but you can also base it on weight:

  • Dogs up to 12 pounds live approximately 14 years, so start annual testing no later than 10.5 years.
  • Dogs 12-30 pounds live approximately 13 years, so start annual testing no later than 9.75 years.
  • Dogs 31-50 pounds live approximately 12 years, so start annual testing no later than 9 years.
  • Dogs 51-80 pounds live approximately 11 years, so start annual testing no later than 8.25 years.
  • Dogs over 80 pounds live approximately 9 years, so start annual testing no later than 6.75 years.

The reality is that when caught early, cancer is easier to treat and we have better chances of preserving life quality (and even extending longevity).

Best to all,

Dr D


Leave a Comment

  1. Patricia Dureja on November 30, 2018 at 10:36 pm

    My 12 year old mixed rottweiler that weighed over 100lbs died back in August from cancer. It seemed that the symptoms came from nowhere just as the article stated but I realize that she had been sick for a long time. My first clue was that suddenly after all those years she began to lose weight like overnight. After taking her to our vet he knew exactly what it was and stated that being dog of her breed, size and age that she had basically run her course. I knew he was most likely right but sought out a second opinion where xrays were taken. Zola lived maybe another week or two from that point. I couldn’t understand how she had just deteriorated so quickly but now it all makes sense. According to the guidelines for weight she actually lived beyond her years and her life was filled with love and happiness. I have never loved a dog the way that I loved my Zola and I miss her dearly. Your article helped clear up a lot of questions that I had. I was the first person that she saw when she opened her little eyes as a puppy. I bottle fed her because she was taken away from her mom way too early. She had knee surgery around age 6 because of her weight & I tried everything that I could to keep her weight down. We made every vet check up possible yet none of us knew until it was too late.. .but just as I was there for her in the beginning I saw her through to her end. It was also I that was there when she closed her eyes for the very last time. What a honor and blessing to have been a part of her life & to have had her in mines.

    • Dog Cancer Vet Team on December 3, 2018 at 7:09 am

      Hello Patricia,

      Thanks for writing, and for sharing your story– it sounds like your girl was well loved. We’re glad that this article was able to clear up some questions for you, and please accept our most heartfelt condolences for your loss

  2. Pam on April 11, 2018 at 5:22 am

    This article really cleared a lot of things up for me. My black lab mix was 10 years old when suddenly she became lethargic. It started with her just having issues with getting up and down we thought it was related to a recent arthritis diagnosis. We had to wait a week before we could get her into a Doctor’s appointment but she didn’t make it that long. Five days after she started exhibiting pain with walking we had to take her to the emergency vet. She wasn’t able to get up at all at that point and I was having to pick her up to take her outside. She was panting heavily and not eating food anymore. I knew that this couldn’t be just pain from arthritis and I knew that it was time to take her to the emergency clinic. That’s how we found out she had some sort of cancer. The vet practically said she was in the end stages of the cancer and needed to be put down. It’s really amazing how my seeming happy and healthy dog could go from acting completely fine to being in absolute misery and pain. I wish I would have seen a more competent Doctor who would have checked her more thoroughly instead just telling me “oh that’s just a touch of arthritis, she’s got a lot of good years left.” That doctor gave me some meds and pushed me out the door. I’m still kind of in shock and wish I would have known sooner 🙁 I will now start getting my dogs screened in their later years so I don’t have to be totally knocked off my feet with a tragedy like this. R.I.P Sweet Pea 🙁

  3. Jade Brunet on June 22, 2017 at 7:20 am

    My dog has been having a hard time sleeping and we are wondering if she could be sick. Thank you for informing about the signs of dog cancer. I did not realize that loss of appetite, vomiting, and weight loss were not actually seen until late in the disease process of cancer. We will pay a visit to our veterinarian to solve any possible problem early on.

  4. suzy000 on October 29, 2016 at 5:10 pm

    My five year old blue eyed Malamute (I know…disqualifying but she was what we wanted….YEP….she is my avatar) was diagnosed with a malignant Mast Cell Tumor yesterday the 28th. You could have knocked me over with a feather when the Doc told me after aspirating the lump on her backside near her spine. I had just told the Doc that I was getting ready to buy a used a treadmill for Mishka to help her lose the weight she put on during the summer months. (She HATES hot weather) but out of caution, I just wanted to verify that the fatty tumor was just that. She came back in the room no longer smiling and said,,,,,”Don’t buy that treadmill”. I instantly became numb. Now we are facing surgery, probably radiation and then more surgery. I refuse to put her through chemo. Radiation is bad enough. This is going to get expensive but I cannot just let her die. She was a gift for my son on Christmas Day when he was 13. He had just lost his Uncle (pancreatic cancer) in June and my brother was like a Father to him. He has a deadbeat Father. Mish filled that void and helped him cope with the loss of my baby brother and now at eighteen…..I cannot stand to see him lose another without giving it my best shot. I have heard of those gofundme sites but it is probably not for pets. Sigh…..what does a single working Mom to do when something like this gets dumped in her lap and I just got the 1st semester of college paid for. I’ll tell you what we do…we work harder and find a way. There is always a way….one just has to be willing to take that leap….I will leap all day if I can protect my family from harm or distress. Well….enough about my challenges…..there are people with many more challenges and on a greater scale than what we are experiencing. They too need our help……and our prayers.

  5. Candice on February 11, 2016 at 7:38 pm

    This makes sense. We had no idea our dog had oral melanoma until her cheek had swelled to a bit larger than a golfball, but before that she had some bad breath which we had brushed off as just old age and her teeth not being in top notch shape. Her vet before this was discovered had actually said soft food can sometimes cause bad breath so to put her on dry food and it would help that. We did as he recommended, but it didn’t help too much and then it started to get worse and finally her cheek started swelling as her breath continued to deteriorate into smelling like death. It happened pretty quickly too and that is when I got very concerned and took her back in to be tested and then we found out she had oral melanoma. They didn’t tell us a stage though, but am sure she was probably around a stage 3 when we took her in. I just feel guilty I didn’t take the first sign of worse bad breath as a cue because if we had of then we may could have extended her life beyond what we are doing now with just prednisone alone. I had been told all my life that brushing an animal’s teeth was not required and their mouthes kept themselves clean in general until recently I started to hear you should brush your dog’s teeth and if not that then check their mouth fairly often and if not that then the vet should at their routine visits. I had absolutely no idea of any of that and her prior vet did not offer to check her mouth and they were mad expensive so we changed her to a new vet who found the cancer and told us all of this. I wish I had known way sooner. Too little, too late in this instance, but if we ever do get another loving pet I will be vigilant about this sort of thing.

  6. Jeff on February 8, 2015 at 1:13 pm

    My yellow lab just turned 8 on feb 6th. He’s been sick for over a month now. All his symptoms cam on very suddenly: vomiting, unable to keep food down, minimal water intake, appears very lethargic at times but has had days where he is his old fashioned self. He has lost a lot of weight from not being able to keep food down. Brought him into the vet 4 weeks ago, all tests were normal despite these sudden symptoms. The vet gave us some moist dog food in which he ate very little. Symptoms were not getting better so I brought him back a week later. X rays were His WBC count was “slightly” high so the vet said possible infection or possible cancer but that she “didn’t have a solid answer” as to what was wrong with my dog. Vet gave us antibiotics to use for a week, they didn’t do anything for him. Another symptom I’ve started to notice is that he will ‘shiver’ in his abdominal region at times but its not consistent. As I stated before, he still has his good days where he is his normal self but he’s only losing more and more weight. I’m at a loss of what to do… some days he looks like he is suffering. I could go back to the vet but I’ve been there twice and paid a lot for the answer of “im not sure I have an answer for you. Any suggestions on a direction to go at this point would be greatly appreciated. Maybe some supplements or new food to try? I’ve read that K-9 immunity plus can help manage symptoms…I’m just not sure what to do. This came on so suddenly and I can’t imagine my life without my best friend.

    • Susan Kazara Harper on February 9, 2015 at 5:43 pm

      Hi Jeff,
      I know this is worrying, and no solid news from the vet doesn’t help. Shivering can indicate discomfort, and ifit’s occasional it’s harder to pin-point. He definitely does not sound happy. What are his poos like? I’m guessing they are a bit lose and if he’s not eating he’s probably not pooing regularly. ?? Does his abdoment seem distended? Is he unhappy when you gently rub his belly? If his tum is tight, distended or he doesn’t want you near, it might indicate there is something going on there. There are so many directions this could go. The first, most basic thing you can do is to give him a week or very simple, very REAL food. Any digestive upset needs a period of bland, useful food. Have you tried to give him meals of cooked brown rice and cooked chicken with chicken broth? It’s the easiest to digest. If you get some boneless, skinless chicken breasts put them in a big pot of water, simmer until cooked, you’ll have plump, moist chicken meat and loads of broth. Cooked brown rice helps bulk it out, but don’t use instant rice. He needs solid nutrition to help regain his balance. You can also scramble eggs and feed them alone, or with the other food. 7-10 days of this food will give him strength from simple, good nutrition, and probably let you know whether it’s a temporary tummy upset or not. I know you’ve spent a lot at the vets, but if you’ve not gotten any more than you’ve shared here, you need a different vet. You may want to try a week of good food as above, and call around to other vets. Remember that they work for you, and you own those test results. If you find a vet you like the feel of, ask your present vet to either give you, or send to the new vet, the x-ray and blood tests and records of treatment. Giving him a week of solid, digrestible real food will tell you a lot. Smaller frequent meals, just as we’d do if our tummy was upset. Start there and let your boy tell you what’s happening by his response. Good luck! and give him a big cuddle from us.

  7. Jessica Rossler on December 10, 2014 at 8:21 am

    My beautiful 8 yr old siberian husky Lilly died this morning from lung cancer, we thought we had more time with her, the cancer came on suddenly, back in November we took her to vet because she wasn’t eating, and loosing weight, he ran blood test and found she had a tick born illness, so she was put on antibiotics. Within the last month, she was getting worse while on them. We had them lower the dose. And she still wasn’t eating, we had to force feed her. She drank fine. Went to the bathroom fine. Then towards the end of November she went down hill. We took her back to vet, because she started having breathing problems. He found a growth in her back leg near her mammary gland. And was going to biopsy after she was done with antibiotics. So while at vet second time. He wanted to check via X-ray how she was, well needless to say, he xrayed, and it wasn’t good, he pulled my bf in back, and showed him the horrific X-ray. She had 6 or so golf ball sized tumors in both lungs, and the vet said prognoses wasn’t good. She was end stage. He didn’t give her long about two -three weeks tops. So she was put on several medicines, and a pain pill. And she was still up and around, very weak wobbly, and still drinking but not eating. So we force fed her, from a syringe the last few days. She had very minimal accidents. Her breathing kept getting worse. So she was given a diuretic. We have two other husky’s at home. And one is her twin sister. We are beside ourselves with guilt, and anger, and we can’t understand how the cancer came on so suddenly. We only had her, and her sister for four years. Before we rescued them, from an abusive situation, they were neglected. And we worked really hard to get lilly to trust again. We gave her all the love and affection we could, took care of her best we could. And we were going to have her put to sleep on Saturday. But God had other plans. And she died at home in our kitchen. I had sure I was there, as I told her we would be with her every step of the way. It’s hard to say goodbye. She was our little girl out of our pups. But witnessing her take her final breaths, and the pool of blood that surrounded her mouth, is something I hoped I would never have to see. I wish we could have done more for her, but chemo wasn’t an option as she was so weak already, and surgery wasn’t an option because she was end stage. So we did the best we could by keeping her comfy, and loved. Should I feel guilty? I’m new to dog cancer, I watched pups I had growing up die. But nothing like this.

    • Susan Kazara Harper on December 11, 2014 at 9:21 pm

      Jessica, everthing about this was horrible. Yet you can not feel guilty. You did everything for her, took her to the vet responsibly at each stage. Sometimes it’s just a lousy, lousy road. When we grieve we beat ourselves up. The time will come when you can make yourself start to remember the years of fun and joy. Yes, I know you wish there could have been more. But you know what, you could have missed them all, too, if you hadn’t had her at all. Know that she was totally happy with you. Dig out the great photos, and please, please believe that the last weeks were just a drop in the bucket of her very good life. Honor her by remembering her well, and maybe get out there and become a voice for dog health and cancer awareness. My two boys put me on this path. I miss them so, but know that what I learned with them can go on to help others. Take care of yourself,

      • Jessica Rossler on December 12, 2014 at 12:40 am

        Thank you so much, Susan! I hope with time we all start to feel better again. She was such a wonderful part of my family. That’s wonderful that you’ve become a voice for dog health and Cancet awareness. I’d love to do that. How do I go about it?
        Thank you again for your kind words, and I hope you have a very merry Christmas and happy joyous new year! Take care


        • Susan Kazara Harper on December 14, 2014 at 9:54 pm

          Jessica, Bless you for wanting to get involved. First, take time to heal. Get through the holidays gently and move into the new year. If you feel motivated to help, there are oh so many ways to share the awareness and knowledge. You’re most welcome to get in touch if you can contribute to this small and passionate team. Give yourself breathing room first, ok?

          Another may come who will need love and help, and you will honor your girl if you find you are able to share her place of joy. All the best, from all of us.

          • Jessica Rossler on December 15, 2014 at 4:32 am

            Thank you so much Susan! It’s not been a week yet. And myself, bf, and daughter are still sad. I’d love to contribute. My other two huskies have been taking things ok. They gloom about the house too. Maybe one day, we will have three again. God bless, have a wonderful and merry christmas, and new year!


  8. Susan Kazara Harper on June 25, 2014 at 5:51 am

    Kim, Please look at If amputation is an option, and the cancer has not metastasized to other parts of Janko’s body, it can be your best option. And dogs do not generally have the problems that humans do with amputation. They already have 3 other legs to rely on, and if he’s limping and not using the leg, he’s already rehabilitating himself. He has youth on his side, and if there is no cancer spread and you’re able to take the cancer away with amputation, you could potentially have many years ahead of you. But Kim, you’ve got to get hold of yourself. The panic and worry are understandable, yet they are not helping Janko. No matter what happens in the coming days, the best thing you can do for him is to give him the just of your calm, loving energy. It’s great that you have a vet you like. Remember, the decisions are yours, and Janko will understand.

  9. Susan Kazara Harper on June 22, 2014 at 12:36 pm

    Did you get in touch with your vet about his symptoms and his medication? Have they told you whether the fibrosarcoma has metastasized? I really, truly know how scared you are, but you can only help him by getting a hold of yourself. Deep breaths. Do you have an oncologist for Janko? You need a specialist, someone who has a lot of experience both with cancer, and with amputation. Get your information, find out what can be done, balance that with what you can afford. No, it’s not fair, but focusing on that is not helping you or him. Remember, YOU decide for him. Others have their training and their opinion, but Janko does not have an expiration date carved in stone. He’s still with you. Monday morning, new day. You can do this. You can do this for him.

    • Kim Adams on June 24, 2014 at 2:25 am

      ive been to the vet a bunch of times…im up all night watching him breath…so afraid he wont wake up with me the next morning…I dont want him to suffer but I dont want to lose him either…I tried to get an oncologist appt, but they didnt have anything til July. I feel like he may not be here come July…the past 2 days he hasnt been eating much, he drank alot yesterday and even played a little in the backyard…this morning he ate very little and puked about a half hour later…I dont want to give up on him but I know I dont have much more money to keep helping him…And that SUCKS, he shouldnt have to die bcuz I cant afford the rest of his treatment…I flip flop about the different avenues to take, do I want to go with amputation and mayb have a few more months, in which he would be miserable recovering from such an extreme procedure. Is that fair to put him thru that for my selfish reasons…Do I wait and put him down b4 he gets too bad..there are no other options…I pray every day, I even went n got holy water for him…some days its like he just doesnt feel good and he will get better and then it smacks me in the face….im going to lose my best friend…my vet is coming to the house thurs. I trust and value his oinion, he is in it to help animals with his whole heart, not for the money. If he tells me he thinks its time I will be saying goodbye to Janko..I kno its my choice and I dont like the choices ive been giving.

  10. Kim Adams on June 19, 2014 at 8:43 pm

    My GSD, Janko will b 2 in Sept. Just a week ago he started limping, like he hurt his paw. It gets worse, his leg started to twist towards the outside n it looked like his shoulder was sticking up….Off to the ER, Wednesday, I thought he slipped his leg out of socket. ..xray said no, but she found a lump on his shoulder…He needed to see a surgeon..I called my vet n got him in the next day, Thursday, since they said they could do biopsy’s n things…What a waste of critiical time…I now had to wait til Monday to see a surgeon…He does n exam n gives options n what he feels is wrong…Hemangiosarioma. .Never even heard of this..Tuesday he has MRI n biopsy, showing the mass to b 23cm x 11cm..I m devastated…im loosing my best friend…Today is Friday, but very early but I m waiting on results as my dog is going down hill fast…I dont want to make a choice until I kno if it is or isnt cancer…But I dont want him to suffer…idk what to do…he just lays around barely walks,eats or drinks…his breathing is rapid as if he just ran a marathon, but sometimes its very shallow…im hoping its the meds making him so out of it n not his life slipping away from me in my sleep….

    • Susan Kazara Harper on June 20, 2014 at 9:07 am

      Take a deep breath. I can feel your panic and that’s completely understandable, but don’t count Janko out yet. You need to get a confirmed diagnosis. It’s unusual that something like this would come on so suddenly if it’s a malignant tumor, but nothing can be ruled out. Hemangiosarcoma is cancer of the lining of the blood vessels, and while it CAN occur anywhere in the body that has blood vessels, the more common sites are the spleen and heart… big, blood working organs. Certainly it’s possible elsewhere. And yes, it’s possible the meds that he’s presently on are causing the rapid breathing and other symptoms you are seeing. You didn’t mention what he’s been given, but please phone your vet back and report these symptoms…. they may need to modify or change his medications. That rapid breathing is no good. I recommend you do that today. If hemangiosarcoma IS confirmed, you can still fight. There is a recommended chemo protocol that may apply… it’s being used more and more with this type of cancer. Called metronomic chemo. But we’ll get to that when you have your diagnosis. GIven the location and that the lump is affecting his leg, you may find that the oncologist (and please try to get an oncologist involved in this to get a complete diagnosis) recommends amputating the leg. This isn’t the end either. Any worries about this, check out But please, please take a breath, get yourself together and let Janko know you’re with him and will do everything needed to help. He is young and strong, so that’s definitely on his side. Download the Dog Cancer Diet from the blog page, and assess his food. He needs real, healing food to help his body cope. Don’t hesitate to call our team on 808-568-3252 if you need to hear a real voice and go through any further information. All the best to you both.

      • Kim Adams on June 21, 2014 at 2:55 pm

        I m still freaking out…biopsy came back fibrosarcoma stage 3…now he started breathing thru his nose tonight…what could that mean…they believe that he should b put down soon. If they remove the tumor/leg, that the cancer would b back within a month. I dont want my dog recovering from a loss limb for the remainder of his time..I feel like that is just too much on him…I m so torn right now….I dont want to lose him…Its not fair..I know I cant afford the therapy, chemo/radiation…I wish I could take his place!!!

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