What Are The Signs Of Cancer In Dogs?

This content was reviewed by veterinarian Dr. JoAnna Pendergrass, DVM.

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Terrier sleeping with stuffed dog (caption: Signs Of Cancer In Dogs)

My wife and I have a dog, and I know the last thing in the world she wants to think about is our pup ever getting cancer. The thought of it can be so upsetting to us that we can blind ourselves and look the other way when it comes to our dogs’ health.

Sometimes the warning signs are obvious – like large growths on the outside of their bodies. Other times, cancers can show up in unexpected ways.

The best thing we can do for our dogs (and ourselves) is to mentally prepare for the possibility of trouble, so we can be proactive at the first sign of cancer in our dogs. Because our dogs can’t tell us what aches and what is irritating them, we have to watch for any odd behaviors or strange sensitivities. We have to make sure that we keep a watchful eye on the things they do every day and try to pick out what seems unusual. More often than not, we have premonitions about when something is bothering our pets, and a lot of times we are right.

What Are The Physical Signs Of Cancer In Dogs?

When we talk about cancer, we often hear the term ‘tumor.’ Although the terms ‘cancer’ and ‘tumor’ are sometimes used interchangeably, they don’t always mean the same thing. Before explaining some of the common physical signs of cancer in dogs, let’s get some clarity around these two terms.

A tumor is an abnormal growth of cells that can be either benign (does not spread to or invade other locations) or malignant (spreads and invades other locations). A benign tumor is not cancerous. Cancer is the malignant form of a tumor.

Dogs can get many types of cancer, so the physical signs of cancer can vary according to the specific cancer type. Here are some common signs of cancer in dogs:

  • Large Growths – Large growths, such as large tumors, can begin to form and should be checked out immediately. It’s especially concerning when these large growths seemingly appear overnight. Take your dog to your vet and have him examined as quickly as possible.
  • Smaller Lumps Under the Skin – Sometimes lumps can develop with age in our pets. Small bumps under the skin aren’t always concerning, but monitor a small bump if you notice one on your dog, especially in the lymph nodes. If it has any changes in appearance (gets bigger, develops uneven edges, turns a different color), take your dog to your vet for a check. Also, if you notice any discharge or bleeding from that area, seek veterinary attention.
  • Odors – Dogs do some pretty gross things normally that will cause odors, but if you start to smell something unusual regularly, it could be an early sign of a problem. These new smells can sometimes come from tumors that could be cancerous.
  • Weight Loss – Significant weight loss over the course of a few months is often a sign of cancer cachexia. Dogs will lose fat and muscle at an equal rate, even if they are eating a normal amount of food.

What Are Common Behavioral Signs Of Cancer In Dogs?

  • Loss of Appetite – Though there can be many reasons your dog might not eat, and one of those reasons could be cancer. When you notice a loss of appetite, the first step should be to  talk to your vet, who can recommend different ways to stimulate your dog’s appetite. For example, bland meals like chicken and white rice will often get your dog to eat again. There are also medications for dogs that can stimulate appetite. If your dog shows a lack of appetite over an extended period of time, it would be wise to get him checked out.
  • Lethargy – Because dogs can’t tell us when something is bothering them, they do a great job of showing us. Those signs will often show up as a lack of energy and an inability to get excited about things that usually make them happy.
  • Changes in Bathroom Habits – Some types of cancer can cause changes in a dog’s urination or defecation. For example, rectal cancer can cause constipation and bloody poop. Bladder cancer makes it difficult for a dog to urinate and causes bloody urine. 
  • Difficulty Walking – Cancers that affect a dog’s limbs cause significant pain and discomfort and make walking very difficult. What used to be an easy walk up and down the stairs becomes nearly impossible for dogs with cancer in their legs.

What Are The Most Common Types Of Cancers In Dogs?

  • Lymphoma: A cancer of the immune system that affects the lymph nodes, spleen, and other organs.
  • Mast cell tumors: A cancer of the immune system that affects the skin and internal organs.
  • Hemangiosarcoma: A cancer of the blood vessels that can affect the skin, spleen, liver, and other organs.
  • Osteosarcoma: A cancer of the bone that is most commonly found in the limbs.
  • Melanoma: A cancer of the pigment-producing cells that can affect the skin and oral cavity.
  • Mammary gland tumors: A cancer of the mammary gland (breast tissue) that is most commonly found in unspayed female dogs.
  • Squamous cell carcinoma: A cancer of the skin or oral cavity that affects the cells that produce keratin.
  • Bladder cancer: A cancer of the bladder that can spread to other organs.
  • Prostate cancer: A cancer of the prostate gland that is most commonly found in male dogs.
  • Leukemia: A cancer of the blood-forming cells that can affect the bone marrow, lymph nodes, spleen, and other organs.
  • Lung Cancer: While less common than other cancers, lung cancer refers to a chest tumor in dogs or a ‘pulmonary’ tumor.
  • Fibrosarcoma: A type of cancer that affects connective tissue in dogs, and it’s characterized by lumps or mass, lameness and pain.

Where Should I Look For Dog Skin Cancer?

Because our dogs are covered in hair, we sometimes forget that they can still be susceptible to different types of skin cancers. However, skin tumors are very prominent in dogs and should be examined immediately when they are first found. While we might think that our dogs are protected, we forget about areas like their noses and the pads on their feet. These areas are extremely sensitive and vulnerable to sun damage.

Skin cancers in dogs include melanoma, which shows up as lumps on the skin or around their mouths, squamous cell cancer and mast cell tumors. Mast cell tumors are the most common skin tumor in dogs and there is no known way to prevent this type of cancer.

Learn more about what to look for in this video:

How Much Can Cancer Treatment Cost?

Papillion laying on ground with toy

Below is a sample claim for cancer from a pet parent and how one pet insurance company covered it.

  • Dog: Bruiser, 11-year-old male Papillon
  • Total Vet Cost: Over $48,500
  • Total Reimbursed By Trupanion: $34,323.95

When I contacted Trupanion after the surgery and spoke to my wonderful claims adjuster and another member of the staff and advised them that Bruiser required chemotherapy and over 20 cycles of radiation, I was told it would be covered. I have to be honest, Trupanion covered all of Bruiser’s surgery, chemotherapy, 22 cycles of radiation, and all follow-up testing and treatment since Bruiser has been in remission well over two years and seven months without any issues. They make me feel like Bruiser and I are not clients but family and are truly concerned that he remains cancer-free.

What Treatment Is Available For Cancer In Dogs?

There are many dog cancer symptoms that have been mentioned already. Abnormalities in behavior or sudden growths under the skin or around the mouth and eyes are easily detectable signs of cancer in dogs. Be proactive and closely monitor your dog to make sure he is happy and healthy. For example, when you’re petting him, feel for spots and monitor anything that seems unusual.

If your dog has cancer, there are things you can do. Talk to your vet, as every case is specific to the current health of your dog. Cancer treatment can broadly be broken down into two categories–medical and surgical–and your vet will determine what treatments would be best for your dog’s type of cancer. There are also supportive therapies, such as high-protein foods you can give your pup to help him battle weight loss.

One example of medical therapy is chemotherapy, which attacks the cancer to keep it from spreading. Another example is medications to reduce symptoms of cancer, such as antiemetics to prevent vomiting and anti-inflammatories to reduce inflammation and pain.

Surgery can remove certain cancers completely from your dog, but make sure you talk to your vet so you understand the risks of such procedures.

Finally, treating cancer in dogs can be cost prohibitive. The average treatment plan (surgery, chemo and radiation) ranges between $6,000-10,000. Pet insurance can help defray this cost. If your dog is uninsured, you might consider pet insurance so that if (God forbid!) your dog does get cancer, you will be financially able to help him battle this horrible disease.

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