How Common Is Cancer in Dogs? Risk and Early Warning Signs

Is My Dog at Risk for Cancer?

Yes, dogs can develop many of the same cancers that affect people. . For example, dogs are the only nonhuman species who can get prostate cancer. According to the National Cancer Institute, approximately 6 million new cancer diagnoses are made in dogs each year. This number likely underestimates the true total, since not all pets receive medical care or a definitive diagnosis. The Veterinary Cancer Society estimates 1 in 4 dogs will develop cancer at some point, and almost 50% of dogs over age 10 will develop cancer. Fortunately, half of all canine cancers are treatable if caught early enough and new treatments are continuously being researched.

What types of cancer are most common in dogs?

Cancer can take many forms and affect the blood, bone, or body tissues. An accurate diagnosis helps determine the most appropriate treatment and prognosis.

Dogs can develop the following types of cancer:

Lymphoma

Lymphoma is one of the most common cancers in dogs and accounts for about 20% of all cases. Dogs are two to five times more likely than people to develop lymphoma. It can affect any breed at any age.

This cancer often appears as swollen lymph nodes under the jaw, in front of the shoulders, or behind the knees. In some cases, lymphoma affects the chest or abdomen, which can cause breathing problems, vomiting, or diarrhea.

Veterinarians often treat lymphoma with chemotherapy. Many dogs respond well and maintain a good quality of life during remission.
Most commonly affected breed: golden retrievers

Mast Cell Tumors

Mast cell tumors typically form on the skin. These tumors can range from relatively benign to very aggressive and may spread to other parts of the body.

Mast cells are immune cells associated with allergies, and veterinarians can usually identify these tumors with a fine-needle aspirate. Dogs with mast cell tumors may show vomiting, diarrhea, or loss of appetite.

Treatment usually includes surgery to remove the tumor. Veterinarians may also recommend chemotherapy or radiation therapy for more advanced cases.
Most commonly affected breeds: boxers and bulldogs

Osteosarcoma

Osteosarcoma is the most common bone cancer in dogs. It occurs most often in large and giant breeds.

This cancer usually affects the long bones in the limbs but can occur in any bone. It progresses quickly and often spreads to the lungs, lymph nodes, or other bones.

Pet owners often notice swelling, lameness, or pain in the early stages. Treatment typically includes amputation of the affected limb followed by chemotherapy.
Most commonly affected breeds: Great Danes, Irish wolfhounds, mastiffs

Melanoma

Melanoma is one of the most common oral cancers in dogs. It appears more often in breeds with dark tongues and gums.

These tumors consist of darkly pigmented cells and can develop in different areas of the body. Oral melanoma often spreads before diagnosis and can be difficult to treat.

Veterinarians may recommend surgery or immune-based therapies depending on the case.
Most commonly affected breeds: Doberman pinschers, standard and miniature schnauzers, chow chows, and Scottish terriers

Mammary gland carcinomas

Mammary tumors are common in unspayed female dogs. They often appear as small nodules near the nipple and may grow over time.

Some tumors are malignant and can spread if not treated. Early surgical removal improves outcomes. Spaying before the first heat cycle significantly reduces risk.
Most commonly affected: older, unspayed females of all breeds

Hemangiosarcoma

Hemangiosarcoma develops from cells that line blood vessels. It most often affects the spleen but can also occur in the liver, heart, or skin.

Dogs with splenic tumors may not show signs of illness until the tumor ruptures. This can cause sudden weakness, pale gums, or labored breathing due to internal bleeding.

Emergency surgery is often required, followed by chemotherapy. This cancer can progress quickly and may not show early warning signs.
Most commonly affected breeds: golden retrievers, German shepherds, Portuguese water dogs, Skye terriers

What are the signs of cancer in dogs?

As with any disease, early detection is critical for the best outcome. Keep an eye out for these early warning signs of cancer in your dog:

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

These signs do not always mean cancer, but they should prompt a visit to your veterinarian.

If you notice changes in your dog’s health, contact your veterinarian. Early evaluation can make a difference.

Use AAHA’s Hospital Locator to find an accredited veterinary practice near you.