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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. Curt on May 21, 2014 at 8:40 pm

    Last weekend my 2 year old yellow lab seemed perfectly normal except for the fact that he had about 5 accidents in the house over the .weekend which was very uncharacteristic. So Monday morning I called the vet to make an appointment thinking he must have a bladder infection or something of that sort. My appointment was for Wednesday morning. By that time I had noticed and mentioned to the vet that since I had originally made the appt. on Monday he had gotten kind of mopey and depressesed looking. So they ran blood test and a urine tests both came back normal. So then they said they wanted to do a thyroid test but the blood had to be sent off to another lab for that one. So we went home and waited for those results, they came back normal. By Thursday night he just laid on the floor and didn’t want to move and actually even threw up as he was just laying there and didn’t lift his head to do so. He eventually got up and went in his kennel and stayed in there the rest of the night. when I went to go get him Friday morning I had to lift one end of the kennel and almost dump him out. I eventually got him to stand up and walk outside and go to the bathroom. After that I took him back to the vef where they kept him there for the day and ran some more test like tick carried diseases and Addison’s disease., again all normal. they also redid the blood tests and found his blood sugar had dropped very significantly since Wednesday, I think they said the level should be around 120 and his was about 30. so they put him on a IV and were able to get the blood sugar level back up to normal but still no change his behavior. Since it was a Friday At the end of the day I had to pick him up and take him to emergency care since they are open nights and weekends. By the time I picked him they had to help me carry him to my vehicle and they came out to my vehicle at the.emergency clinic and took him in on a stretcher. Saturday I had gotten a couple calls from the vet saying they are not finding any reason for his comditionn and wanted to do a ultra sound. Got a call back from a tech saying the vet wanted to come In and talk to him. Sure enough the ultrasound revieled a grape fruit size tumor in his admonmen. So long story longer I had to make the hardest’ saddest decision ever and say goodbye. Again this was a 105 pound 2 year old strapping dog who exactly 2 weeks before was at the lake swimming and running around with absolutely sign of anything being wrong. I hope nobody else ever has to go through but just in case if they do I hope they come across this story and it can help them diagnose it quicker then I dead because looking back the ultrasound was $150. If I/the vet would of started there it would saved about $2,000 in other test and overnight care, etc..

    • Susan Kazara Harper on May 22, 2014 at 12:08 pm

      Curt, we are so, so sorry to hear your story, and sad for your shocking loss. Thank you for sharing it, because as you said it may help someone else. It sounds like what happened occurred so quickly that there was very little you could have done even if the mass had been discovered quickly. But you did your best at every stage for your boy and he knew you were looking out for him. Please take care.

  2. gia holdridge on February 4, 2014 at 3:37 pm

    my dog died yesterday of dog cancer r.i.p hershey a black pug that was 5 was the most loving dog ever

    • Susan Kazara Harper on February 5, 2014 at 1:11 am

      Dear Gia, I am so sorry that Hershey moved on. I truly know your pain and the empty space in your heart and your home. It will take a long time to mourn, and to turn the sadness of these last months into smiles as you remember all the years of joy you shared. It really stinks, I know, to lose him after only 5 years. Perhaps there is a higher reason, but that may come later. Please don’t make his memory a sad one. When you are able to, celebrate him.

  3. Dawn Reeves on September 12, 2013 at 6:10 am

    No one can diagnose my 10 year old Cockapoo. Signs include lethargy, anorexia, weakness, subjective fever. Initial lab (which was normal 3 weeks prior, aside from globulin) shower WBC 13, Hct 33, nml platelets, albumin 1.9, globulin of 5 (had been 5.4 3 weeks before and gone unnoticed by Vet). Did abdominal u/s, found nothing but some chronic renal changes. U/a with 1+ protein, globulin electrophoresis is polyclonal. Ascites started developing. She developed respiratory distress and some purpuric type lesions on her back along the spine. Hct dropped to 26; plts stable, albumin stable. Was started on high-dose Pred for 3 doses then I stopped it bc she wasn’t better at all and I was worried about infection. Started doxy (rapid tick assay all neg). About to tap ascites but resolved (48 hours after Pred and 24 hours after doxy). So was restarted on low dose pred (anti-inflammatory dose at 0.5 mg/kg/dose). 24 hours later dramatically better. Several small nodules in her back leg – that they were unsuccessful at aspirating – have now virtually disappeared and feels like only a small lymph node.

    My fear is that she has an occult malignancy and we are only temporizing the situation


  4. BEBE4LOVE on August 19, 2013 at 1:10 pm


  5. Lisa on May 13, 2013 at 12:56 pm

    I have 10 year old neutered male pug. he has had Addison’s disease since he was 1.5 years old. His Addison’s is well controlled with .3 ml percorten every 28 days and .5 mg. prednisone every other day. We found a mass that suddenly appeared on the sheath of his penis. I took him in the next day and the vet removed it. It came back as a Grade 3 MCT with a high micotic index. It was removed with clean margins. he was on benadryl and tagamet before we found the tumor, so we continued with it. My vet ordered Kinavet and in the mean time we did a high dosage prednisone treatment. he has now been on Kinavet for three weeks (100 mg. daily, he is 19.2 lbs.) and Apocaps (2 caps twice a day). We have found no new growths. he had bloodwork done a week ago and it was good. But last night he stopped eating. he would not take food or his pills. He throws up undigested food from nearly 24 hours ago, which makes me worry he has pancreatitis or something. My vet says to give him a break from the Kinavet and see how he does. When he last threw up it was orange, I assume from the curcumin in the Apocaps. How well does Kinavet play with Apocaps and are either contraindicated in dogs with well-controlled Addisons disease?

    • Dr. Demian Dressler on May 30, 2013 at 4:20 pm

      Hi Lisa
      Sorry to hear about your pug’s mct. 🙁
      how has the response been to stopping the kinavet?
      We have not had problems with addisonian dogs btw..
      let us know,

  6. Magda Gryczmanska on May 13, 2013 at 8:09 am

    Dear Dr. Dressler

    My 11-year old greyhound developed a mole just above his elbow which grew rapidly over last couple of months and is black. I have also found a pinhead sized mole which looks exactly as the now black mole did in the beginning (mauve coloured). He chewed on the black one and when I took him to the vet he was prescribed antibiotic and cream as it looked infected and bled. It healed after a couple of days. The vet confirmed that the growth is located in the skin – she was able to put her fingers underneath. When I discussed the options with the vet who thought it could be a wart or a tumour she said that the mole was hard and therefore not suitable for biopsy. I have read on the Internet that biopsy is a standard procedure and no one mentioned that a biopsy cannot be taken from a firm growth. Should I insist?

    • Dr. Demian Dressler on May 30, 2013 at 4:21 pm

      Dear Magda,
      no, one can biopsy a hard mass. Perhaps she was talking about a fine needle aspirate?

  7. Lori Swanson on May 11, 2013 at 4:08 pm

    Our jack Russell terrier was diagnosed with cancer under the tongue it was on the very back of his tongue underneath .Found out on A Wednesday He had his entire tongue removed on Friday we are now faced with how to get him to be able to eat. He wants to eat but the food falls right out of his mouth our vet assures us that he will figure this out any suggestions???

  8. Karen Reinhold on April 27, 2013 at 3:13 pm

    My little Pomeranian just passed away a couple of hours ago. I feel a hole has been punched in my chest. I didn’t think he had cancer. He started to not want to eat last week, but up until that time he was his usual playful self. I took him to my vet because I thought he might have gotten some fertilizer on him that my apartment put down. My vet did some blood work, and his liver results showed really high. The first vet said they couldn’t feel any lumps. They gave me some medication for his liver, but it didn’t seem to help. He would drink water, but didn’t want to eat. I took him back to the vet and they did an xray. They found a mass the size of a grapefruit. Just as we were discussing what to do, a nurse called the doctor and said my dog was dying. Within about a minute he was gone. I always took him to the vet for his regular shots etc. I just don’t know why it was never found earlier. I’m going to miss him so much!

    • Dr. Demian Dressler on May 9, 2013 at 3:38 pm

      Dear karen
      I am so, so sorry to hear about your little pom..
      I really am sending you my condolences and am so sorry.
      Dr D

  9. Chris on October 20, 2012 at 7:24 am

    My family has had our dogs died from cancer. the first one was a golden lab he was about 11 years old. I remember he couldn’t eat for two weeks and i think moth or two or more after that, the vets said he had cancer but they didn’t see it when they went in the first time.
    R.I.P Luc

    Thunder my mom got remarried and he was a rotwiller he had cancer on his butt and they tried to removed it but they put him to sleep it came back.
    R.I.P Thunder

    Harley was a yellow lab we had him since he was a puppy about 2004 My dad got him for me, He was put to sleep at the age of 8 years old. He didn’t have any signs of any cancer the last two weeks i also went to hang out wit him.

    He was not feeling good this week and he was taking to the vets and this poor dog didn’t deserve to go this soon. I was hoping for two more years at least.

    R.I.P Harley

    the other dog my mom had was a rotwiller that not died from cancer but everytime he was eating it just come out the other end he couldn’t gain weight so it was a birth defect or something.
    R.I.P Bud (can’t spell his name bearrine or something like that.

  10. Elissa on October 3, 2012 at 4:38 am

    My @10 year old (rescued) female Lab, Addie, suddenly developed severe diarrhea a few days (no blood), but still very strong appetite, no vomiting, etc. Her liver numbers are always elevated a bit because of the Rimadyl she’s been on, but the vet’s second-in-command said the chilling words ‘RIDDLED WITH CANCER” yesterday, because her abdomen was enlarged. Xray showed nothing. Gums, breath, eyes are clear. Her energy is strong (even though she’s a big girl, having been a backyard breeder before she came to us). We’re now taking her to an internist DVM to figure out why the diarrhea and to see if the other vet’s diagnosis is remotely accurate. Prayers, please. She’s our big yellow baby girl.

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