Signs of Cancer in Dogs

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Cancer is the number one disease that kills our pets, and being educated is key to keeping your canine companion as healthy as you possibly can. In this article, we will look at several signs that your dog has cancer, although there’s no need for you to worry just yet. Be mindful and be on the lookout for these possible symptoms, and seek medical assistance if you notice them.

Almost everyone knows that the quicker cancer is diagnosed, the better the chances of it being completely treatable. Annual check-ups are important, but if you have any suspicion that there might be something going on, you should take your dog to the vet before that time comes along.

Common Signs of Cancer in Dogs

As you might imagine, there are many types of neoplasms that can affect our beloved canine friends, and it’s quite difficult to create a set of general and somewhat universal symptoms that you should pay attention to.

For example, signs of skin cancer in dogs largely differ from those that indicate the possibility of your pet having stomach cancer. Nevertheless, we’ll do our best at highlighting some warning signs your dog has cancer.

Skin changes

You pet your dog every day, and if you do that anyway, it might also be a good idea to make sure that you look at and touch almost every body surface to make sure that nothing new is there. You don’t have to perform a physical examination of your canine buddy.

But even so, it’s safe to say that you might feel lumps or bumps if you interact with your dog daily. The important thing here is to avoid giving your dog pats on the head alone – sometimes, you need to pet your dog’s body as if he or she were a cat. Only in that way will you be able to feel anything weird.

Another indication that there might be more to what you see is that your dog has a sore that’s just not healing, no matter what you do. Lesions that are itchy or painful and don’t go away aren’t a good sign.

Weight gain or weight loss

While some gastrointestinal tumors trigger weight loss, others can cause bloating or weight gain. Sudden weight gain can be a sign of stomach cancer in dogs, and if your dog seems to be eating less but bulking up, you need to take your dog to the vet. Even a sudden spike in appetite could warrant a visit. There are also tumors that develop for years and years, and that might grow in several different organs. Due to their size, they actually take up space in the animal’s abdominal cavity, giving you the feeling that your dog is putting on weight when in fact he only has a distended abdomen.

As for weight loss, it is perhaps the number one sign of cancer in dogs. Gastrointestinal tumors are known to grow rapidly, so if you notice that your dog keeps eating or has the same appetite, but he’s actually losing weight, something wrong is going on. Of course, this could also mean that your Fido has a serious parasite infection, in which case it might be better than cancer, but you still have to take your dog in for a check-up.

Seizures and collapsing

General lethargy, weakness, as well as collapsing are some dog cancer signs and symptoms you should be able to notice. In some large breeds, these clinical manifestations can be a sign of spleen cancer, but they can be caused by a variety of other medical conditions, including old age. If your dog just doesn’t get up like he or she used to and doesn’t greet people, as usual, there might be something happening. If your dog collapses, take him to the vet right away – even if you feel like he’s going to be okay the next day or if he recovers quickly.

Seizures are never good signs. They can be an indication of brain tumors and can be typically encountered in older dog cancer patients. If your dog has uncontrolled and sudden bursts of activity like jerking, champing and chewing, or he/she begins foaming at the mouth, take your dog to the vet right away.

Mouth changes

Your dog’s mouth can give you a lot of information that you might not even be aware of. Oral tumors aren’t that hard to notice if you pay attention, and what you should be on the lookout for are any changes in shape, size, or volume – lumps, sores, changes in gum color, and even bleeding.

Even the fact that your dog’s mouth seems to smell more or differently than it usually does is a possible indication that there might be more to what you’re seeing. If you do not brush your dog’s teeth regularly – although we highly recommend that you do since this routine can prevent periodontitis – you can at least pay attention to your buddy’s mouth whenever he/she yawns. Most oral tumors are diagnosed far too late, and a sign like your dog not wanting to eat because chewing food is too painful might be an indication that the cancer has already reached a more advanced stage.


While it can be a sign of cancer, coughing isn’t necessarily and automatically associated with this disease. Small breed dogs can develop coughs since they have a variety of windpipe problems. Besides, coughing can also be a sign of a respiratory infection, not cancer. If a cough continues for several days, disappears, and then comes back time and again, it’s time to take your dog to the vet.

Any changes in bathroom habits

Diarrhea and vomiting should never be overlooked, and although they might not be highly specific signs of gastrointestinal cancer, they can sometimes be just that. Occasional diarrhea isn’t a sign of cancer, but if it persists or seems to be coming back without any reason whatsoever (like changes in diet), you have to at least take your dog in for a check-up.

Blood in the urine and stool should always tell you that something is definitely not right. Think of it this way – if they were to happen to you, you would be rather alarmed, wouldn’t you?

Bone cancer

Although it might be somewhat less common compared to gastrointestinal tumors, for example, this type of cancer is still possible and can be encountered in some of our canine friends. Some signs of bone cancer in dogs that you should pay attention to range from lameness and pain to lethargy, weakness, and swelling around a particular area of a leg.

Because bone neoplasms can show up anywhere, you could notice a swollen upper or lower jaw, pain when opening the mouth, and nasal discharge, or you could notice signs in a completely different body area, like a leg. Osteosarcoma of the ribs can rapidly spread to the lungs, in which case you would notice difficult and painful breathing.

Bone cancer is typically a disease that shows up in middle-aged to older dogs, with larger breeds being more predisposed to it. Great Danes and Saint Bernards are about 60% more likely to develop osteosarcoma compared to dogs whose weight is under 65 pounds, and large breeds like Labrador Retrievers and Irish Setters are about eight times more predisposed to it than small breeds.

Final thoughts

If you see any of these signs in your canine companion, don’t automatically assume that he or she has cancer. Cancer is only diagnosed following an extensive series of tests from blood work to imaging methods like ultrasonography or X-rays and even a CT. A definitive diagnosis can be established thanks to biopsy and cytology.

You might have noticed that some of the symptoms we described aren’t necessarily specific to cancer, and that’s why you shouldn’t go into a panic and believe that your canine friend has this unforgiving disease. The important thing to keep in mind is that you need to pay attention to your pet and notice any changes in his or her behavior, feeding, and general wellbeing. Get pet insurance because it can definitely help if your dog needs treatment for any type of medical condition.



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