12 Signs Your Dog May Have Cancer: Don’t Ignore Them

Fight Against Canine Cancer

Dog and Cat Cancer Awareness

In this new post we will be looking at 12 signs your dog may have cancer.

Are there really signs your dog may have cancer? The short answer is yes, but a more in depth answer would be that the signs for cancer can also signal the presence of other diseases, as symptoms can be similar. It is also worth noting that signs will vary depending on the type of cancer your dog is afflicted with.

For that reason I always encourage anyone who sees changes in their dog’s behaviour or physical appearance, no matter how slight, to see their vet sooner rather than later. 

How common is cancer in dogs?

It seems that cancer is responsible for about half of all deaths in dogs over the age of 10. Dogs can get the same types of cancers as humans, but they metastasize at a much faster rate, meaning time is not on their side, and procrastination can lead to a very sad outcome, very quickly.

Examples from my own life

Since I have never had a dog with cancer, I will use three of my cats who did have it as an example, and you will see how the signs were completely different in each.

Tyler Had Oral CancerOne of my cats (her name was Tyler) had oral cancer, and it was discovered because I noticed what looked like a piece of dried food on the side of her mouth, but she would wince whenever I tried to get at it. After taking her to the vet we discovered she had cancer, and had to have part of her jaw removed. Had I waited much longer, there would not have been enough jaw to save, and she would not have survived. No other treatment was required, and she adjusted very well, very quickly. She lived a few more years after that, until the cancer had spread to the bone under her eye. That was discovered because her eye was tearing constantly.

Another cat (Night Night) had been losing weight, and couldn’t settle for long. He was constantly getting in and out of his litterbox, peeing, trying to pee…. My vet initially treated him for a urinary tract infection, as the slight presence of blood indicated. When it didn’t clear up after a second course of antibiotics, an ultrasound found a tumour, and TT and Night Night Both Had Cancersadly there was nothing more to be done.

TT (Night Night’s brother) developed cancer a few years earlier. I bring up this example to show the importance of checking your dog for lumps and bumps. One day I was petting him, and felt a lump on the side of his neck almost the size of a ping pong ball. I may be exaggerating slightly, but not by much. He was all black with tons of fur, and there’s no way you could have eyeballed that.

It was a very fast growing tumour, that I am sure was not there long because I always pet my animals and would have noticed. It could not be operated on as it sat on his carotid artery, so chemotherapy was our only option. A few rounds shrunk it enough, and a course of chemo meant it took longer for the tumour to re-grow, until it stopped working. A second drug had an effect, though not for long. After that we let him be, and sadly he died a few weeks later. It was a very aggressive form of cancer, with a poor prognosis from the start.

These are just 3 examples of how different cancers will manifest themselves in different ways – some obvious, some not.

How do I know if it’s cancer?

Below I will provide you with a list of signs that, if your dog is showing any of them, should mean a vet visit as soon as possible.

To answer this question though, you don’t. The very best advice I can give, and have given in my previous posts is this – if you notice any changes in your dog’s behaviour, no matter how subtle, don’t make the mistake too many pet parents of senior dogs make.

Not everything can, or should be, attributed to the natural ageing process, and only your vet and modern medicine, can help distinguish between what is “normal” and what is not.

Cancer can be very fast acting, so you don’t want to wait to have it checked out.

Here are the 12 signs that should lead to a vet visit

Lumps or bumps on, or under, the skin

Get into the habit of petting your dog (I know you already do, but this time you have an ulterior motive!!) and check for any lumps or bumps. This includes his face, ears…

Weight loss

Sudden weight loss in a dog whose diet and eating habits have not changed, is a cause for concern.

Changes in appetite

Lack of interest in, or difficulty eating does not necessarily signal cancer, but dogs (and cats) don’t stop eating without a reason.

Unusual or offensive odours

Foul odours coming from anywhere on your dog’s body (mouth, ears, nose or anal region) can signal a tumour.

Pale gums

It’s good to know what your dog’s mouth looks like when he’s well, so you will know if there are any changes that could signal illness. For example, pale gums could indicate blood loss, and cancer is one of the illnesses linked to this sign.

Lethargy/loss of stamina

There is a difference between a senior dog slowing down, and true lethargy. You know your dog, so if he is spending more time sleeping, not so playful, lost interest in walking, speak to your vet. Again, this does not prove he has cancer, but combined with other signs, can be worrying.

Changes in bathroom habits

Peeing more often, difficulty peeing or pooping, presence of blood, even accidents in the house.

Open sores or wounds that don’t heal

Open sores or wounds that aren’t healing, could be signs of conditions such as a skin disease or infection, but….

Evidence of pain

Limping, lameness, stiffness when your dog walks, unwillingness or inability to jump on the couch like he used to and the like, are typically the result of arthritis, which is very common in senior dogs. However, there is also the possibility it is the result of cancer, especially bone cancer.

Respiratory problems/ difficulty breathing

Coughing, shortness of breath, general difficulty breathing can indicate heart disease as well as cancer.

Vomiting, diarrhoea, bleeding or discharge

Vomiting, diarrhoea, and/or bleeding and/or discharge from any part of your dog’s body needs to be checked out immediately.

Behaviour changes

Behaviour changes include some of the signs listed above, in addition to things like spending more time away from everyone, snapping, aggression. These behaviours can mean your dog is experiencing discomfort, or outright pain.

Fight Against Canine CancerAny other signs or indications?

That’s the thing. Sometimes there are no signs, or should I say no obviously visible signs, like my cat with the tumour in his neck. There were no changes in behaviour, or anything else that would have made me think there was a problem – and I am very vigilant when it comes to paying attention to behaviour changes in my animals.

Putting your mind at ease

I know how intense this article is, and how easy it is to jump into panic mode, but just because your dog shows some of these signs, does not mean he has cancer.

12 signs your dog may have cancer – conclusion

I’m not one to say don’t worry because of course you will. All I am saying is – don’t live with the panic, just go and take some action. Make an appointment to see your vet, as soon as possible and if he’s busy and it will take a few days to be seen, stress to them your concern over the signs you have observed.

I can be quite persuasive, and often end up crying – not on purpose for effect, that’s my blind panic shining through and I can’t stop it, and they usually squeeze me in.

I know this post on the 12 signs your dog may have cancer can be frightening, but seeing any of them shouldn’t make you panic, just see your vet so you can find out what’s going on.


12 Signs Your Dog May Have Cancer: Don’t Ignore Them

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8 thoughts on “12 Signs Your Dog May Have Cancer: Don’t Ignore Them

  1. It’s true.the best thing when we see some anomalies is to wait for something to happen, action sometimes may save our pet’s life. I have a routine to cuddle my pets very often and check them, I also am very careful in their diet,as i found out a lot of cheap industrial dog\cat foods often a cause of cancer.
    Thank you for the article

    1. Hi Andrea, thanks for taking the time to leave a comment. It’s a good idea that you check your pets often. I never would have found that lump in my cat’s neck if I hadn’t been petting him. You’re right about your pet food concerns – there are lots of articles citing studies that have proven the link between poor quality pet food and all kinds of illness and disease.

  2. Hi,
    Very good topic. My daughter has a wonderful Australian shep/lab mix. Sadie was found in a homeless shelter for dogs when she was about 1-year-old by my daughter who was looking for a small apartment lap dog. She took one look at Sadie and fell in love. Sadie was a puppy mill puppy and developed some pretty serious health issues now that she is in her later years. She is the most loving and caring animal I have ever known. I have some arthritis and so I tend to fall behind when my daughter, her daughter and my -son-in-law go for walks. Though Sadie can keep up with them, she always volunteers to stay behind and accompany me to the end of the trail. No one tells her to. She just knows that is what she should do. Love her, love her, love her. I guess what I am saying is, if anyone is afraid to take a puppy mill puppy because of health issues later in life, it is a factor, but there is nothing that can prepare you for the love that these beautiful little creatures can and impart. Thanks for your blog and for reminding us to watch our pets carefully.

    1. Hi Elizabeth, thanks for sharing, and few things make me happier than hearing rescue stories. My husband and I rescued a puppy mill dog. She was kept in a chicken coop, breeding for 8 years. The shelter staff said they had never encountered such a terrible case. She would pee if you looked at her. Sadly we only had her 9 months before she died from what I believe to be veterinary incompetence. Thankfully in the time she knew love, and started to trust me enough to finally pet her after 7 months. I wish people would care enough like your daughter did, to adopt a homeless animal. People don’t realise they’re most likely buying a puppy mill dog when they choose to shop instead of adopt.

  3. Hello Hindy.

    A few days ago a good friend discovered her little pooch has got a disease similar to cancer with quite a few of the symptoms you mention here. Sadly, nothing can be done for her dog which is only 5 years old and may, at a push, last 1 or 2 years more.

    Because she checks her dog regularly she had previously mentioned these symptoms to her vet here in the UK but was told they could just be a short term infection. It was on the second check-up 3 months later, 4 days ago, she got the bad news.

    Now she has to make a decision as to whether to keep her pooch alive in the best state of health then let him go, or whether to extend life by a couple of very uncomfortable months due to serious side effects that would make the dog’s life nasty for him.

    May I ask you opinion here, as you have obvious unwell-dog experience?

    Many thanks – Andre

    1. Hi Andre, what a sad situation for your friend to find herself in. I can relate. You say he may be okay for another year or two, but then you mention treatment extending his life by a couple of months. It’s not quite clear. It’s true, I do have lots of unwell dog and cat experience, but it would not be my place to offer an opinion on what your friend should, and should not, do. First let me say I hope she has a vet she trusts. If she doesn’t, she may want to find one and get another opinion. I’ve had two different vets (I live in England as well) responsible for the death of 2 different dogs, so I recommend she make that a priority. She needs to have this conversation with him, and be clear on what life would be like for her dog, with and without treatment. Like I said, it isn’t my place to offer an opinion, but personally I always consider what’s best for my animal, not for me. I also rely a lot on the opinion of my vet. I hope she finds the answers she needs.

  4. Some great advice and things to look for in both cats and dogs.
    My question to you, how did you come to do training in Toronto? Did you live here at one time? I’m just outside of Toronto, which is why I’m curious.

    A pleasure to meet your acquaintance, I’m going to add you to my feed of blogs to read. 🙂

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