5 Most Common Cancers In Dogs Based on Vets’ Experience

Like humans, dogs are also susceptible to various types of cancers. We may be able to prevent the onset of such conditions, however, in some cases, the causes may be unknown.

To gain more in-depth knowledge on this topic, we approached 4 veterinarians to share some insights with us based on their experience

Read on to learn about the most common types of cancers, causes, symptoms, treatment, care and prevention methods as advised by experts!

We’d like to give special thanks to the following veterinarians for their insightful contributions:

  • Dr. Sarah Reidenbach (DVM) from Ruthless Kindness,
  • Dr. Joanna Woodnutt (MRCVS) from DoggieDesigner,
  • Dr. Sara Ochoa (DVM) doglab.com
  • Dr. Leslie Brooks (DVM) from betterpet.

  • This article has been reviewed by Eliezer Bauzon, Pet Lovers Centre’s in-house Pet Care Consultant.

    *Disclaimer: The advice offered in this article is not meant to replace the advice of vets. Do make sure to consult a vet for accurate diagnosis and advice on your dog’s condition.

    Common Types Of Cancer In Dogs

    Cancers can often present themselves in the form of benign or malignant tumours. Thus, this article seeks to share about the most common types of cancers and malignant tumours that can plague a dog.

    These cancers were pointed out by the abovementioned veterinarians based on their experience and the frequency of occurrence among canines.

    Types of CancerOriginates InCommonly Found In/OnSymptoms
    LymphomaLymphocytes• Lymph nodes
    • Spleen
    • Bone marrow
    • Exhaustion
    • Appetite loss
    • Vomiting
    • Diarrhoea
    Mast cell tumourMast cells, found in body tissues• Skin
    • Liver
    • Intestine
    • Lumps
    • There may be redness and swelling around the lump
    MelanomaSkin or mouth• Skin
    • Mouth
    • Toenails
    • Lumps
    • Swollen toe
    OsteosarcomaBone cells• Any bone• Lethargy
    • Loss of appetite
    • Lameness
    • Swelling
    HemangiosarcomaCells in blood vessel walls• Spleen
    • Liver
    • Heart
    Located Internally
    • Lethargy
    • Loss of appetite
    • Weight loss

    Located externally
    • Lumps
    • Swelling


     Most commonly found in: lymph nodes, spleen, bone marrow

    Lymphoma, which is the cancer of the lymphocytes and lymphatic system, is a common type of cancer in dogs. It can account for up to 25% of all canine cancer cases according to Dr. Sarah Reidenbach (DVM).

    The dog may show signs of exhaustion, appetite loss, vomiting or even diarrhoea when suffering from this type of cancer.

    Mast cell tumour

     Most commonly found in: skin, liver, intestine

    Mast cells (a type of white blood cell) affect a body’s allergic response, which can then form cancerous tumours.

    Mast cell tumours fall under the category of skin cancer and typically manifest as nodules on the skin. The tumour can spread to other areas of the body such as the liver and intestine. 

    It can be graded based on a number of ways, such as the size of the tumour, the types of cells found during a biopsy and how far it has spread.


    Dog paw with red patches

     Most commonly found in: skin, mouth, toenails

    Melanoma is a type of skin/oral cancer that involves tumours. The tumours can be located in the mouth, on the skin, or on the toenails. Those that are found on the skin and toenails are typically malignant.

    The growth affects the pigmented cells and can spread throughout the body. There may be swelling, pain and even infections around the tumour.


     Most commonly found in: any bone

    According to Dr. Reidenbach, osteosarcoma is a common cancer among canines that affects the bone. The tumour may occur on any bone in the body and is one of the most painful and aggressive cancers. 

    Dr. Joanna Woodnutt (MRCVS) shared that dogs diagnosed with osteosarcoma tend to survive for an average of two months. The treatment is typically focused on improving the dog’s quality of life rather than extending their life. Thus, it’s sometimes seen as one of the deadliest cancers in canines.


     Most commonly found in: spleen, liver, heart

    Hemangiosarcoma is the cancer of the cells of blood vessel walls. It can spread rapidly and occur anywhere in the body. However, the growth is most commonly located in the spleen, liver or heart. 

    The tumour, which is filled with blood, is prone to rupturing which causes the dog to suffer from a loss of blood. Thus, Dr. Reidenbach cites the cancer as a “ticking time bomb”.

    Causes Of Cancer In Dogs

    White dog with black patches around eyes lying with eyes closed in the arms of a human

    Cancer in dogs can be due to age, genetics or environmental factors.


    The risk of cancer in dogs typically increases with age. According to Dr. Reidenbach, this could be due to the dog’s weaker immune system, extended exposure to carcinogens and the higher chance of cell mutation.

    However, Dr. Woodnutt shared that lymphoma is an exception to this observation, as the risk of this type of cancer decreases after 6 years of age.

    Genetics: Dog Breeds That Are More Prone To Cancer

    Past experience from veterinarians such as Dr. Leslie Brooks (DVM), have shown that certain dog breeds are more susceptible to certain types of cancer. 

    For example, Boxers are more likely to get mast cell tumours and histiocytomas. Golden Retrievers are also more susceptible to lymphoma.

    Environmental: Second-hand Smoke Exposure

    Second-hand exposure to smoke is detrimental to the health of dogs, just as it is for humans. Dr. Woodnutt commented that inhaling second-hand smoke could place dogs at a higher risk of nose and lung cancer.

    Environmental: Agricultural Chemicals

    Dogs may come into contact with agricultural chemicals as they step on lawns or sniff the ground with their snout. These toxic chemicals may increase the risk of cancer.

    Environmental: Prolonged Exposure To The Sun

    Dogs with light fur have an increased chance of developing skin cancer if they are exposed to the sun for a prolonged period of time. This is especially so if they expose areas like their belly to the sun, where it’s sparsely coated.

    Symptoms Of Cancer In Dogs

    Symptoms of canine cancer may include

    • Abnormal or rapidly growing swellings
    • Sores that don’t heal
    • Loss of appetite and weight loss
    • Bleeding or discharge from body openings
    • Difficulty eating, swallowing, or breathing
    • Lameness
    • Difficulty urinating or defecating

    Treatment For Cancer In Dogs

    Doctor in purple conducting surgery on a dog

    The four main types of treatment for canine cancer include

    • Surgery
    • Chemotherapy
    • Radiation therapy
    • Immunotherapy

    The treatment options will depend on the type and stage of the cancer.

    Caring For Dogs With Cancer

    How To Tell When Your Dog Is In Pain

    It can sometimes be difficult to tell when your dog is in pain. 

    Below are some signs you can look out for to know that your fur friend is suffering. 

    • Limping
    • Pacing
    • Excessive panting
    • Refusing to lie down 
    • Difficulty breathing
    • Lack of appetite
    • Loss of interest in the people, toys and activities they’ve always enjoyed

    What To Feed Dogs With Cancer

    White dog with brown ears lying on a blanket next to a window with eyes closed

    When it comes to feeding dogs with cancer, it is important that they have a sufficient intake of nutrients. 

    Below are some basic recommendations that can be taken into consideration.

    • Relatively low amounts of simple carbohydrates
    • Moderate amounts of fats, particularly omega-3 fatty acids
    • Proteins with fat such as chicken, turkey, pork, fish and eggs

    However, it’s important to note that diet recommendations differ for each dog and cancer type. 

    Dr. Sara Ochoa (DVM) shared that certain dogs may require canned food, human food, or extra treats to encourage them to eat.

    How To Prevent Cancer In Dogs

    Spaying Your Female Dog

    Spaying female dogs can help to reduce the risk of breast cancer significantly. According to Dr. Woodnutt, dogs that are spayed after their second heat cycle are 86% more likely to have breast cancer than those who have done so earlier.

    However, spaying could potentially result in an increased risk of other cancers such as osteosarcoma.

    Avoid Exposure To The Sun

    To reduce the risk of dogs suffering from skin cancer, they should be kept out of the sun during the hottest hours of the day. If you expect that they’ll be exposed to the sun for an extended period of time, you could consider the use of sunscreen specifically for pets.

    Avoid Exposure to Chemicals

    You can help your dog avoid contact with these toxins by using alternatives to agricultural chemicals such as organic fertilisers. You can also avoid letting them walk on the lawns of other house owners.

    Supporting Dogs With Cancer

    Cancer treatment and visits to the vet may lead to a huge financial strain for pet owners. 

    Purchasing pet insurance may be helpful in making the treatment more affordable as it covers surgery, chemotherapy and other forms of cancer treatment expenses. This, therefore, ensures that your pet can obtain the maximum support in their fight with cancer.


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