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6 Most Common Types of Cancers in Dogs (Vet Answers)

Dr. Joanna Woodnutt, MRCVS (Vet) Profile Picture

By Dr. Joanna Woodnutt, MRCVS (Vet)

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Unfortunately, our canine friends can be affected by cancer, just as we can. According to The Veterinary Cancer Society, as many as one in four dogs in the USA will be diagnosed with cancer during their lives. The risk of cancer in dogs increases with age, and sadly it is one of the leading causes of death in older dogs. The outlook isn’t all bleak, however- with early detection and medical advances, many cancers can now be successfully managed.

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What is cancer in dogs?

Cancer is a disease whereby a group of abnormal cells divides uncontrollably, known as a tumor. Cancer can start from any cell in the body, and the symptoms and outlook depend partly on the cell they arise from.

Some tumors are ‘benign’. This means that they do not damage surrounding tissues and do not spread to other parts of the body. However, they may grow and, depending on where they are, this can still cause a problem.

Others are ‘malignant’. This means that they move into and damage surrounding tissues, and they may spread to other parts of the body (‘metastasize’). Malignant cancers tend to be more serious and harder to treat.

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Image Credit: Ruth Black, Shutterstock

What are the signs of cancer in a dog?

As with humans, there are many different cancers a dog can get. This means cancer can present in a number of different ways. Some of the most common symptoms of cancer in dogs include:

  • New lumps or bumps
  • Wounds that won’t heal
  • Skin lesions (areas of hair loss or weeping sores for example)
  • Sickness and/or diarrhea
  • Lack of appetite
  • Difficulty swallowing
  • Unexplained weight loss
  • Drinking excessively
  • Lethargy (a lack of energy)
  • Trouble going to the toilet
  • A bad smell
  • Abnormal discharges

It is important to remember that these symptoms can also be caused by many other, often harmless, illnesses. So, if you notice one of these symptoms in your pet, there is no need to panic, but do seek veterinary attention promptly.

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The 6 Types of Cancer Dogs Can Get:

1. Mast Cell Tumor

mast cell tumor in labrador retriever dog
Image Credit: John McAdorey, Shutterstock

What is a Mast Cell Tumor?

Mast Cell Tumors (MCT) have been found, by many studies, to be the most common skin tumors in dogs. They arise from mast cells, which are part of the immune system. MCTs can be anywhere on the spectrum from almost benign to very malignant.

What are the symptoms of a Mast Cell Tumor in dogs?

A new mass or lump, which can sometimes be quite flat. With more aggressive forms, as well as a skin mass, dogs may develop sickness, diarrhea, and a lack of appetite. This is due to an excess of histamine circulating through the body, which is released by the mast cells.

What is the treatment for a Mast Cell Tumor in dogs?

Treatment for a mast cell tumor is surgical removal of the mass and sending it to be examined by a pathologist laboratory. If the MCT is ‘low grade’, then removal can be curative. If it is ‘high grade’, further surgery and chemotherapy or radiotherapy may be needed as well. If the tumor cannot be removed due to its size or location, there is a treatment available to try to shrink the tumor.

What is the prognosis for Mast Cell Tumors in dogs?

This depends on the grade of the tumor and whether the tumor has spread to other parts of the body. For low-grade tumors, the outlook is excellent. Sadly, high-grade MCTs that have spread to other parts of the body can carry a poorer outlook.

2. Lymphoma

What is Lymphoma?

Lymphoma is a cancer of the white blood cells, which circulate in the blood and lymphatic system (part of the immune system).

What are the symptoms of Lymphoma in dogs?

Lymphoma can arise anywhere, since the blood vessels and lymphatic system travel all around the body. Symptoms will vary depending on which part of the body the lymphoma is affecting. For example, lymphoma in the gut could cause digestive symptoms such as sickness and diarrhea, whereas lymphoma of the skin could cause skin lesions.

The most common symptoms of lymphoma in a dog are enlarged lymph nodes (glands), which you would feel as lumps under the chin, in front of the shoulders, or behind the knees; unexplained weight loss; decreased appetite; reduced energy levels, and increased thirst.

What is the treatment for Lymphoma in dogs?

Unfortunately, lymphoma cannot be cured. So, the treatment is aimed at making your dog feel well or better for a period of time. The treatment is chemotherapy alongside ‘palliative care’ (medications to improve quality of life by treating any symptoms your dog may be experiencing). Some people choose not to treat lymphoma in dogs, but your veterinarian would discuss all options with you if your dog was diagnosed.

What is the outlook for Lymphoma in dogs?

Sadly, the outlook is poor for long term survival. However, lymphoma can often be successfully managed, giving the dog a good quality of life for a period of time.

3. Osteosarcoma

What is Osteosarcoma?

Osteosarcoma is cancer of the bone. Unfortunately, it tends to be very aggressive. The cancer usually spreads rapidly to other areas of the body; often the lungs, lymph nodes and/or other bones. It is more common in older, large, or giant breed dogs.

What are the symptoms of Osteosarcoma in dogs?

Swelling and severe pain are usually the first symptoms. This can present as a limp or non-weight bearing lameness, meaning the patient would be walking on three legs. Common sites for osteosarcoma are around the shoulder and knee, but they can be found anywhere in the bones.

What is the treatment for Osteosarcoma in dogs?

Because it is so aggressive, amputation (surgical removal) of the affected limb is usually the treatment, alongside chemotherapy. Sometimes ‘limb-sparing’ surgery is an option, where only the affected part of the bone is removed. Radiotherapy is one option for providing pain relief if surgery is not performed. As with all cancers, treatment is a very personal choice and one that your clinician would guide you through.

What is the outlook for Osteosarcoma in dogs?

Unfortunately, osteosarcoma is an aggressive cancer and the outlook is poor. Even with amputation, dogs generally don’t live more than a few more months. The aim of treatment is to alleviate pain, and chemotherapy can also prolong life expectancy.

4. Hemangiosarcoma

What is Hemangiosarcoma?

Hemangiosarcoma is cancer of the blood vessels. It is most commonly found in the spleen, but it can be found anywhere.

What are the symptoms of Hemangiosarcoma in dogs?

Unfortunately, these tumors often show few symptoms until the tumor bursts, causing blood loss and symptoms of shock. These include weakness, panting, a fast heart rate, pale gums, and collapse.

What is the treatment for Hemangiosarcoma in dogs?

Surgery to remove the tumor is often possible, especially if the tumor is in the spleen. Sadly, the tumor has often spread to other parts of the body by this time. Chemotherapy can be used alongside surgery to try to increase survival time.

What is the outlook for Hemangiosarcoma in dogs?

Sadly, even with treatment, the outlook is generally poor. The average survival time with treatment is around 3-6 months.

5. Mammary Tumors


What is Mammary Gland Carcinoma?

Mammary gland carcinoma is malignant breast cancer in dogs. It usually affects female dogs and is more common in females who haven’t been neutered (‘intact’ or ‘entire’ dogs). In dogs, around 50% of mammary tumors are benign and 50% malignant. The malignant form often spreads to other areas of the body, usually the lungs.

What are the symptoms of Mammary Tumors in dogs?

The first symptom is usually a lump within the mammary chain, near the nipples, or in the breast tissue. These are often firm and irregular (bumpy). The masses may ulcerate and bleed or become infected. They are sometimes warm and sore to touch. If the cancer has spread, symptoms include reduced activity, weight loss, breathing problems, or coughing.

What is the treatment for Mammary Tumors in dogs?

Treatment is surgical removal of the mass or masses. Sometimes one or even two sides of the chain of nipples need to be completely removed (‘mastectomy’). The mass will be sent off to be tested, to see whether it is malignant or benign. Intact females are often spayed at the same time. Chemotherapy with or without radiotherapy may also be offered if the tumor has spread.

What is the outlook for Mammary Tumors in dogs?

With benign or low-grade tumors, surgical removal can be curative. For malignant tumors, the outlook will depend on the grade of the tumor and whether it has spread.

6. Melanoma

What is a Melanoma?

Melanoma arises in the pigment-producing cells of the skin. It can be found anywhere on the skin but is often found in or around the mouth. Other common sites include around the eyes and around the footpads.

What are the symptoms of Melanoma in dogs?

Melanoma often presents as a dark-colored lump on the skin or in the mouth. They may also be raised, flat areas. Oral melanoma (in the mouth) may present as difficulties eating or bad breath. Around 80% of oral malignant melanomas spread to other areas of the body.

What is the treatment for Melanoma in dogs?

Treatment is surgical removal where possible, alongside treatment for any spread. This can involve chemotherapy, radiotherapy, or immunotherapy.

What is the outlook for Melanoma in dogs?

The outlook for melanoma depends on how quickly the cancer is treated and whether it has spread. Without treatment the outlook is poor, and the cancer can be fatal in only a couple of months.

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Final Thoughts

Naturally, the thought of cancer in your canine friend is both daunting and terrifying. As with humans, there are many types of cancer that a dog can be affected by. The treatment and outlook will depend on the type of cancer.

Early detection is important with any cancer and can affect the outcome. So, if you notice anything about your pet that you are concerned about then it is important to see your veterinarian as soon as you can.

There are many new cancer treatments becoming available, which can improve quality of life and sometimes life expectancy. It is important to remember that these decisions are personal to you and your pet, including the decision as to whether or not to treat. Your veterinarian will be able to guide you through all of the available options and help you to make informed decisions.

Featured Image Credit: ewka_pn, Pixabay

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