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5 common cancers in dogs

In the US, Cancer is the leading disease-related cause of death for dogs. Here we discuss common cancers in dogs and their signs.

5 common cancers in dogs

Cancer is the leading disease-related cause of death among dogs in the US. The Veterinary Cancer Society ranks cancer as the leading cause of death in 47% of dogs—especially those over 10 years of age. To help in the effort to educate pet owners about these malignancies, November has been designated National Pet Cancer Awareness Month.

As with cancers in humans, early detection has a profound influence on outcomes. Here are some cancers commonly seen in dogs, as well as some ways you can help spot the trouble signs early. 

Blood (Lymphoma)

Lymphoma is a form of malignancy that affects white blood cells. There are more than 30 types of lymphomas that commonly affect dogs, and together they account for about 7% to 14% of all cancers seen in canines.

Commonly observed symptoms of lymphoma in dogs may include:

  • Enlarged, firm lymph nodes (especially under the jaw and behind the knee)

  • Loss of appetite

  • Lethargy

  • Weight Loss

  • Swelling of the face or legs

Lymphoma can manifest in other ways as well. For example, cutaneous lymphoma can appear as dry, raw, or itchy patches on the skin; whereas gastrointestinal lymphoma can manifest as vomiting, diarrhea, and weight loss. Since many of these symptoms are not exclusive to lymphoma, contact your vet as soon as possible to obtain a diagnosis.

Editor’s Note: Finding lumps all over your dog can be terrifying. Veterinarian Dr. Lee Pickett shares the best action plan for lymph node cancer in dogs.


Skin abnormalities are fairly common in dogs, and not all are indicative of cancer. As in humans, malignant melanoma is among the most common and affects the pigmented cells of the skin. In dogs, most malignant melanomas occur in the mouth or mucous membranes, though these cancers can develop quickly and may spread to other regions of the body.

Symptoms of skin cancer in dogs include:

  • Black, brown, dark gray, or red patches (under 2.5 cm in diameter)

  • Skin anomalies in pigmented areas such as the mouth, lips or feet

  • Raised wart-like bumps on the belly or groin (squamous cell carcinoma)

  • Slow-growing or ulcerated tumors (mast cell tumors)

If you notice any of these on your pet, consult your vet as soon as possible to confirm or rule-out a cancer diagnosis.


Mammary (breast) cancer in dogs affects approximately 25% of unsprayed adult females, but this risk can be greatly reduced (to about 0.05%) if your animal is spayed before reaching first estrus. If spayed after first heat, the risk for mammary tumors is 8%.

Signs of breast cancer in dogs include:

  • Bloody discharge or pus from nipple

  • Multiple bumps

  • Painful or swollen breasts

  • Singular lumps

  • Ulceration 

  • Yellow discharge or pus from nipple

There are different types of breast cancer, including adenoma, sarcoma, carcinoma, fibroadenoma. Your vet can confirm the diagnosis and will work with you to develop a treatment plan.

Head & Neck

Head and neck tumors seen in dogs can be the result of various cancer types, Unfortunately, these cancers can be quite aggressive, and their proximity to blood vessels, nerves, sense organs, and other structures can make treatment problematic. As not all head or neck masses are malignant, any such tumor should be evaluated by your vet as soon as possible to confirm or rule-out a cancer diagnosis.

Signs include:

  • Any abnormal mass on the head, face ore jaw

  • Oral tumors

  • Difficulty eating or swallowing

Bone (osteosarcoma)

The most commonly seen bone cancer in dogs is osteosarcoma, with tumors occurring most often in the large bones of the limbs. Unfortunately, bone cancers can spread to other areas of the body, such as lymph nodes and lungs.

Common symptoms include:

  • Joint or bone pain

  • Swelling

  • Lameness

  • Lethargy or reluctance to exercise

We hope this fact sheet helps you make more informed choices about the care and medical treatment of your dogs.

Editor’s Note: We all want our pets to live long, healthy, active lives. Yet each day in America, pets suffer from health issues that could have been prevented. These seven pet parent tips can help your dog or cat live its best life.

Cecily Kellogg is a pet lover who definitely has crazy cat lady leanings. Her pets are all shelter rescues, including the dog, who is scared of the cats. She spent eight years working as a Veterinary Technician before becoming a writer. Today she writes all over the web, including here at Figo.

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