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Updated May 11, 2021 – Sometimes it starts with a misstep or subtle lameness. Or a small lump on the leg that becomes tender to the touch. Or a dramatic, sudden fracture.

Osteosarcoma is the most common primary bone tumor of dogs and nearly 10,000 dogs are diagnosed with this cancer each year. Osteosarcoma accounts for 85% of all primary malignant bone tumors of dogs and tends to affect the limbs more commonly than the spine or skull.

Recognizing signs, understanding risk factors and knowing about treatment options can help you give your dog a better quality of life, even with a cancer diagnosis.

Demographics, signs and diagnosis

Osteosarcoma can affect any dog at any age, but there are some identifiable risk factors. These include:

  • High-risk breeds
    • Boxer
    • Great Dane
    • Rottweiler
    • Saint Bernard
    • Irish setter
    • Doberman pinscher
    • Greyhound
    • German shepherd
    • Irish wolfhound
    • Leonberger
  • Height (which often tracks with larger breeds)
  • Increased weight (another variable that can coincide with breed)
  • Older age

A recently published study took a different angle when looking at breed susceptibility for osteosarcoma. The research team grouped dogs based on genetic similarities rather than as individual breeds when determining risk. For example, in this study the mastiff-terrier group (which includes boxers, golden retrievers and mastiffs) had the highest incidence of osteosarcoma. One conclusion reached by the research team was that veterinarians and owners might want to take extra care if a dog is a member of a susceptible group and has a sudden lameness.

Another ongoing debate revolves around the effect of timing of spay/neuter on the incidence of OSA. Some studies suggest that earlier age at spay/neuter is a risk factor for disease, but other studies show the opposite. All agree that more research is needed, and the Foundation’s Golden Retriever Lifetime Study is following cases of osteosarcoma in the enrolled dogs closely to add critically needed data to this important question.

The most commonly reported signs of osteosarcoma include:

  • Lameness
  • Swelling or “lump” growing on a limb
  • Sudden bone fracture

X-rays are helpful in making a diagnosis of osteosarcoma and to rule out other common causes of lameness. Unlike bacterial or fungal infections, which can affect both bones of a particular joint, osteosarcoma does not cross a joint – this can be a tip-off that a patient has a bone tumor and not an infection.

Despite physical examination findings and X-rays suggestive of cancer, it can still be unclear if a bone abnormality is due to osteosarcoma, a different type of cancer, or another disease affecting bone, such as infection. A bone biopsy may be necessary to make a definitive diagnosis.


The treatment of osteosarcoma almost always begins with amputation of the affected limb. Although many owners are understandably upset and concerned about amputating a limb, most dogs do very well with surgery. Because osteosarcoma is a painful disease, amputation also provides relief from unrelenting discomfort that is hard to control with pain medication alone. However, the prognosis remains poor with surgery alone; 90% of dogs will die of this disease within one year if surgery is the only treatment attempted.

Chemotherapy can help prolong remissions, with some dogs living years after amputation and chemotherapy. But these success stories tend to be the outliers, not the norm, and odds are still poor for long-term survival. Osteosarcoma spreads quickly, usually to the lungs, and nearly 90% of dogs have metastases by the time of diagnosis, even if there are no obvious signs of disease spread.

Morris Animal Foundation makes a stand against osteosarcoma

Morris Animal Foundation has been a leader in trying to find new, innovative therapies to treat osteosarcoma. We recognized that more work needed to be done on all aspects of osteosarcoma, from understanding the basic mechanisms of tumor spread to better treatments. Although we’re making steady progress, we’ve got a long way to go to unlock the secrets of this painful and deadly cancer. Learn more about ways you can help ensure that dogs live healthier, happier and longer lives!