Pet Wellness Guides > Cancer In Dogs | Signs, Types, Causes & Treatments

Cancer In Dogs: Signs, Types, Causes & Treatments

Posted: 11/06/2023 | BY: Content Writer | Categories: Uncategorized


Almost all of us can name at least one person in our lives who has battled cancer. Unfortunately, we can probably say the same for dogs. According to the American Kennel Club, nearly one-third of dogs over seven years of age will experience cancer at some point.

As frightening as it is to receive a diagnosis of cancer in your dog, the disease is often very treatable. With approximately six million new cancer diagnoses in dogs every year (according to the National Cancer Institute), it is important for dog owners to be familiar with the signs of cancer and various treatment options.

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Cancer in Dogs

Cancer is defined as “uncontrolled growth of abnormal cells,” but cancer is a very complex and complicated disease. The way the disease presents itself can look very different in each individual dog for a variety of reasons, from age to breed to type of cancer and beyond.

What causes cancer in dogs?

Given the complicated nature of cancer, and the fact that reliable data is difficult to obtain due to differences in reporting requirements in animals versus in humans, it is hard to say what causes cancer in dogs.  Some believe factors like genetics, environmental toxins, solar radiation and hormones can play a role in causing cancer.


Signs of Cancer in Dogs

The first indication of cancer in dogs is often an unusual growth or lump/bump that persists or grows over time. These growths can appear anywhere on the body.

Other signs of canine cancer include:

  • Loss of interest in play/exercise
  • Sores that won’t heal
  • Sudden, unexpected weight loss
  • Loss of interest in food
  • Choking or other problems eating
  • Unexplained bleeding, vomiting, diarrhea or discharge
  • Unexplained odor
  • Prolonged limping or stiffness

Talk with your veterinarian if your dog develops any of these issues.

See your vet immediately if your dog experiences:

  • Wheezing or difficulty breathing
  • Straining to go to the bathroom

It is important to note that any of these problems can be a sign of a variety of illnesses and do not automatically indicate that your dog has cancer. The only way to obtain an accurate diagnosis is to see your vet regularly, and especially when you notice something about your dog that concerns you.

How is cancer diagnosed?

Your veterinarian will likely order blood tests to rule out other conditions and possibly perform an x-ray or ultrasound to look for internal growths. To definitively diagnose cancer, a biopsy will likely need to be performed to examine the tissue under the microscope and determine a more specific diagnosis.


Common Types of Cancer in Dogs

Studies show that cancer in dogs tends to develop similarly to cancer in humans. So, your dog could develop lung, stomach or pancreatic cancer just like people can.  Some of the most common types of cancer in dogs are:

  • Lymphoma (cancer of the lymph nodes)
  • Mast cell tumors (cancer formed in the mast, or immune, cells in the skin)
  • Melanoma (skin cancer)
  • Osteosarcoma (bone cancer)
  • Mammary gland carcinoma (similar to breast cancer)
  • Hemangiosarcoma (cancer of the cells that line the blood vessels, most often affecting the spleen, liver, skin and heart)
  • Soft tissue sarcomas


Symptoms of Canine Cancer

Symptoms of cancer can vary widely based on the type and severity of the dog’s cancer.

Some of the symptoms of the most common cancers include:

  • Lymphoma: Swollen lymph nodes, vomiting, diarrhea, difficulty breathing (if swelling presses on lungs or abdominal organs)
  • Mast cell cancer: Vomiting, diarrhea, loss of appetite
  • Osteosarcoma: Pain and swelling in the affected limb(s)

Is cancer painful for dogs?

Your dog will likely experience some sort of pain as a result of cancer or its treatment. Some pain can be short term, such as when a tumor pushes on organs or nerves, or can occur as a result of radiation, chemotherapy or surgery. Some pain could be more chronic and related to the type of cancer. It is important to recognize your dog’s pain signals and inform your veterinarian or veterinary oncologist to best manage your dog’s pain.


Dog Breeds Most Affected by Cancer

Reliable data related to breeds most affected by cancer is difficult to find because each veterinary office has a different system (or no system at all) of tracking cancer diagnoses. Additionally, some dogs may not receive a formal cancer diagnosis at all, so data that exists can easily be inaccurate.

While all dog breeds are susceptible to cancer, some cancers occur in only certain breeds.  For example, Bernese mountain dogs are one of the few breeds known to contract a rare type of cancer known as hystiocytic sarcoma.

Other cancers are more likely in dogs with certain physical characteristics. Melanoma, for example, tends to be more likely in dogs with dark tongues and gums. Additionally, mammary gland carcinomas are most likely in female dogs who have not been spayed.

It is believed that mixed-breed dogs may have a higher incidence of cancer than purebred dogs.


Treatment for Cancer in Dogs

Cancer treatment for dogs varies greatly based on the type of cancer, symptoms, whether or not the cancer has spread and other factors that naturally make dogs different.

Your vet will likely refer you to a veterinary oncologist who can discuss further options with you.

Canine cancer treatment options include:

  • Surgery: If your dog has a large growth, your veterinarian may want to perform surgery to remove it and have it tested to see whether or not it is malignant.
  • Radiation therapy: Radiation therapy involves directing concentrated radiation at affected cells to stop the growth and shrink or kill what cells exist. In order to get the most precise radiation treatment, your dog will need anesthesia.
  • Chemotherapy: Chemotherapy is drug therapy that works to kill dividing cancer cells and stop cancer from growing or spreading. Your dog will receive chemotherapy through pills, injections or an IV in the vet or veterinary oncologist’s office.
  • Immunotherapy: This is a growing treatment option, as a variety of research is being conducted. Immunotherapy basically involves getting your dog’s immune system to fight the cancer itself. Vaccines are one way immunotherapy is conducted, and a melanoma vaccine already exists for dogs.

In addition to treating the cancer, your dog’s provider will likely want to treat the symptoms that result from the treatment and the disease itself in order to give your dog the best quality of life possible. These include pain management, nutrition, exercise, etc.

How long can dogs live with cancer?

It is nearly impossible to say. While some cancers can be very aggressive and cause rapid decline in your dog’s health, others can be completely cured through surgery. Your veterinary oncologist will be able to give you the best estimate as to what you can expect for your dog’s particular cancer and circumstances, but even that is just an estimate.


Cost of Treatment

Unfortunately, cancer in dogs is an expensive condition to treat. Costs vary, of course, but the most effective options for treating cancer are also some of the most expensive treatments out there for dogs. According to the American Kennel Club, chemotherapy treatment alone can cost anywhere from $3,000 to over $10,000.


Prevention of Cancer in Dogs

As with nearly all medical conditions, close monitoring of your dog’s health overall is the best preventative measure a pet owner can take. Also, similar to many other medical conditions, early detection is vital. While it is difficult to prevent cancer, early detection and treatment can provide the best chances of a positive result.

Here are some things pet owners can do to help insure that cancer is detected as early as possible:

  • Take your dog for check-ups with her veterinarian regularly. Once a year is essential, and some vets recommend every six months for older dogs.
  • Check your dog for lumps/growths regularly and monitor them for growth or any other abnormality. This can be done during petting/cuddling or as part of your grooming routine.

One of the few ways to truly prevent cancer is to have female dogs spayed before their first heat cycle, which prevents a significant preventer of mammary gland carcinoma.


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For information on other common dog health problems, read our article 31 Most Common Dog Health Problems.



  1. American Animal Hospital Association. (2020). Is My Dog at Risk for Cancer? Retrieved from
  2. American Veterinary Medical Association. (2020). Cancer in Pets. Retrieved from
  3. Boehme, K. (2020). Cancer and Pets: What’s the Cause? Retrieved from
  4. Gibeault, S. (2017). Cancer in Senior Dogs–Signs and Symptoms to Watch For. Retrieved from
  5. Merck Manual: Veterinary Manual. (2020). Caring for a Pet with Cancer. Retrieved from

The information contained on this blog is intended for informational and educational purposes only and should not be construed as medical advice. It is not a substitute for professional veterinary care. Always consult with your veterinarian before making any changes to your pet's health care or treatment plan.

The authors of this blog are not veterinarians and do not claim to be experts in pet health. The information provided here is based on our own experiences and research, as well as information from reputable sources. However, we cannot guarantee the accuracy or completeness of this information.

We encourage you to do your own research and consult with your veterinarian before making any decisions about your pet's health.

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