Symptoms of Dog Cancer

Learn more about some common symptoms of canine cancer to safeguard your dog's health and wellbeing!

As cancer is getting more and more prevalent in our canine friends, we need to be as vigilant as we can in observing our dogs and trying to detect any abnormalities that may have developed in our dogs.

Some symptoms of dog cancer are non-specific and rather indistinct and, especially at the onset of the disease, it is difficult to tell whether a dog showing some cancer-like symptoms is in fact suffering from canine cancer or some other illnesses.

It is helpful, therefore, to get ourselves familiar with some common symptoms of cancer, and at the same time, learn about some other more common disorders that may cause similar signs.

Common Symptoms of Dog Cancer - or Not

The following signs are often shown by dogs suffering from cancer. However, they may be caused by some other forms of illnesses as well.

Lumps and Bumps

Weimaraner Different forms of cancer (e.g. lymphomas, mast cell tumors, fibrosarcomas) can arise as lumps and bumps on a dog's skin.

Dog parents naturally become alarmed if they find lumps and bumps on their dogs. The good news is, not all bumps and lumps are cancerous. Very often, benign growths such as warts, fatty tumors, cysts, etc. can arise in a dog's skin as well.

So how can we tell whether a lump is benign or malignant? Usually, any lumps and bumps that appear, then decrease in size or even disappear, and finally reappear in a larger size are more likely to be cancer than benign lumps. However, the only way to tell for sure whether a lump is cancerous or not is by a quick and painless process called fine needle aspiration, in which a needle is used to extract some cells from the lumps for examination under the microscope.

Coughing and Sneezing

While coughing and sneezing can be symptoms of dog cancer, there are also quite a few other dog illnesses that have the same symptoms.

Acute coughing is usually caused by some kind of allergies or infection (e.g. kennel cough), while chronic coughing may be caused by heartworm infection, fungal infection of the lung, or heart disease.

Sneezing can also be the result of allergies. However, if the sneezing is accompanied by a bloody nasal discharge from only one side of the nasal cavity, and it has been ruled out that there are no foreign bodies (e.g. foxtail) trapped up the dog's nasal cavity, then cancer should be suspected.

Vomiting and Diarrhea

Chronic gastrointestinal problems such as vomiting and diarrhea can be symptoms of cancer of the GI tract, or cancer anywhere else.

There are, however, several dog illnesses that can cause the same symptoms. The most common one is inflammatory bowel disease (IBD), and another possibility is Addison's disease. It is important to have an early diagnosis of whatever disease the dog is suffering, since chronic inflammation of the GI tract may eventually progress to cancer.

Appetite Loss

Appetite loss is one of those dog cancer symptoms that is indistinct, as many other diseases (e.g. dental or gum diseases, IBD, heart disease, kidney disease, to name just a few) can cause appetite loss in dogs as well. Also, older dogs tend to eat less. If you notice that your dog is suddenly losing his appetite, try to look for and convey any other accompanying symptoms to your vet so that a proper diagnosis can be made at the earliest possible time.

Chronic Skin Disease

Skin problems, such as skin sores, itch and lesions, and wounds that do not heal, can be indicative of canine skin cancer. However, bacterial or fungal infections or immune disorders can also cause these symptoms.

Blood in Urine or Urinary Incontinence

These symptoms can be caused by some types of dog cancer (such as bladder cancer), but they can also be caused by urinary tract infections, bladder stones, kidney disease, diabetes, Cushing's disease, etc.


While cancer can cause a lot of pain to a dog, so can many other diseases, such as arthritis, ear infections, dental or gum diseases, etc.


Bone cancer can cause a dog to limp. However, lameness can also be caused by arthritis, hip dysplasia, or some form of injuries.

Lethargy and Weakness

Perhaps this is one of the most vague symptoms of all diseases! Dogs with cancer do, understandably, become lethargic and weak. However, a dog can be lethargic due to a zillion other reasons, e.g. pain from arthritis, anemia, fever caused by infections, and so on.

It is therefore important to look for and tell your vet any other accompanying symptoms that you may find.

Bad Breath

Oral cancer in dogs can cause bad breath, but perhaps more frequently, bad breath is caused by indigestion, dental/gum diseases, liver disease, and kidney disease.


Brain tumors can cause seizures, but so can thyroid problems, kidney disease, liver disease, hypoglycemia, and poisoning.

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The Bottom Line

As you can see, a lot of the above symptoms are not unique to cancer. That is exactly why very often cancer is not diagnosed until it is at a later stage.

The bottom line is, whenever a dog has a disorder that does not respond well to treatment in one to two months, and is showing some symptoms of dog cancer, then the possibility of cancer should be considered and a more thorough examination should be requested. Reject the suggestion of adopting a "wait-and-see" attitude. Timely action can save your dog's life!

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