Signs of Cancer in Dogs: What to Look For

signs of cancer

Our dogs are family members. We laugh with them, celebrate momentous occasions, and watch them enjoy life. When we think of the idea of them getting an illness like cancer, it is absolutely devastating. While dogs are susceptible to the same types of cancers as humans, they can metastasize at a much faster rate. It is an unfortunate fact that half of all dogs over the age of 10 will develop some sort of cancer in their lives. Pay attention to the signs of cancer just in case.

While the thought of cancer is scary, noticing the signs of cancer early is important. Dogs routinely live past the age of 10, showing just how far veterinary medicine, as well as pet care, have advanced in recent years. Just like in humans, half of all cancers are curable if they are caught early. That’s why it is extremely important to know what signs of cancer to look for in dogs so we know when to seek medical help.

Common Signs of Cancer in Dogs

Unexplained Weight Loss or Gain

If you notice that your dog is losing weight either rapidly or slowly without a reduced diet or exercise, call the veterinarian. A cause of this could be a tumor along the intestine. This is the most common sign of cancer in dogs. Also, sudden weight gain or bloating could signal a serious problem. If the dog is maintaining his or her regular appetite and exercise routine, yet is gaining weight, make an appointment with the veterinarian.

Collapsing, Weakness, or Lethargy

If your dog should collapse, seek medical help immediately. Collapsing, weakness and general lethargy can be signs of cancer in dogs. If your dog falls down, and then seems better the next day, still seek help because this can indicate a tumor of the spleen. If you notice unusual behavior, you may want to call the veterinarian. For example, if your once happy and excited dog suddenly seems to lose interest in activities they once enjoyed or perhaps stops greeting you at the door each day, this could be a sign of cancer. Keep in mind that lethargy is different from fatigue. Excessive sleep and delayed responses to visual and auditory stimuli can indicate a problem, so if your dog suddenly seems a lot less active for an extended period of time, seek help.


While coughing isn’t always a sign of cancer in dogs, a persistent cough that lasts for more than a few days could be a cause for concern. It may be a sign of lung cancer.

Changes in the Mouth

It is a good idea to take a look inside your dog’s mouth every few weeks, perhaps when they yawn or eat. If you notice sores, lumps, a strange odor, bleeding, or a change in gum color it can be a sign of oral cancer, particularly in older dogs. Often, this sign goes unnoticed. Check regularly, especially if you have a dog of advanced age, and notify the veterinarian if you see any changes.


Nosebleeds in dogs are never normal. Particularly in older dogs, this could signal cancer of the nose. However, no matter the age of the dog, if a nosebleed occurs, seek medical help.


Seeing your dog have a seizure can be extremely distressing. As this can be a sign of a brain tumor, notify your pet’s doctor immediately if you see your dog having sudden and uncontrolled bursts of activity, like chomping and chewing, jerking of the legs, or foaming at the mouth.

Changes in the Skin

Make a habit of checking your dog’s skin frequently. If you notice lumps, bumps, or any sort of change, it can be signs of cancer. Whether benign or cancerous, it is best to find it early and have it treated, so be mindful of changes when you pet your dog. Also look for sores that won’t heal or lesions that seem itchy or painful. This can indicate abnormal cell growth. If you notice abnormal lumps or swellings that persist or continue to grow, call the veterinarian.

General Pain or Signs of Discomfort

No one knows your dog better than you do! If he or she seems to be in pain, such as if they cry out when touched, or just seem uncomfortable, make an appointment with the veterinarian as soon as possible. Signs of discomfort when eating can signal mouth cancer, so be aware of this as well.


Persistent discharge from the nose or eyes can indicate a problem. If you notice a nasal discharge or eye discharge, call the veterinarian immediately. These signs can signal facial or eye tumors.

Sudden Lameness

Lameness presents as tenderness and subtle pain, limping or favoring a limb, or in severe cases, the inability to place any weight on the limb. It refers to any changes in your dog’s gait. If you notice pain that persists, it could be a sign of bone cancer, so have it checked.

Unusual Bowel Movements

You see your dogs output each day, so be aware of anything that doesn’t seem normal. Persistent diarrhea, hardened stools, and straining can all be symptoms of illness. In particular, if you notice black, tarry stools, call the vet immediately as this can signal a tumor.

Difficulty Breathing or a Change in Bodily Functions

A common sign of cancer in dogs is when normal bodily functions become painful. If you notice difficulty breathing, straining, or any signs that the dog is uncomfortable during normal activities, this could be a warning sign. Call the veterinarian as soon as possible.

Noticing the early signs of cancer is one of the first steps in helping your dog live a long, healthy, and active life. Always provide an appropriate diet, exercise and mental stimulation for your pet. Whenever you notice anything unusual, don’t hesitate to get it checked out by an expert veterinarian. Early detection is best, especially in dogs of advanced age. Always track your dog’s health, and seek help when needed. The professionals at Tipp City Veterinary Hospital are here to help, so contact us with any questions you may have.

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Google Reviews
Judy Bayes
Judy Bayes
posted 2 months ago

Highly recommend!!!
Annie, my Golden Retriever Mix, is not a patient there, but got both her Flu vaccines at Tipp City Vet.
The First one, was at their drive up clinic and the second one at their office.
Both were fantastic experiences! The staff (Dr Jim Mathias, the Vet Techs, and Front office) were all super friendly, professional, and great with Annie! And they were very accommodating too, as I had to change my appointment a few times, in order to fit my ever changing schedule.
If I didn’t already have a vet that I love, and am very loyal to; I would definitely make the 30 minute drive to their office!

Lena Kellerman
Lena Kellerman
posted 4 days ago

I really like this place. The staff is always really friendly and willing to help with any questions or concerns I have. I usually see Dr. Ken and he treats my cats nice even if my cats don't lol. I just had to take one cat in due to constipation twice in a year. We got out in roughly an hour and they gave me a list of things to try without spending a lot of money.

Mike Quakenbush
Mike Quakenbush
posted 1 month ago

Always happy with the staff. Lots of space so the pets can have their own space. The most honest Dr.s ever. These people truly care, they aren’t just trying to make money off of you. They want what’s best for your pet.

posted 1 week ago

Excellent treatment by all the staff. Got a phone call telling me how my cat had done during her dental cleaning. Very happy with the service from all staff. and Patches is home and doing great!!

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