Primary Bone Tumors in Dogs and Cats: Signs, Diagnosis, and Treatment

Bone tumors are among the most common tumors in dogs but are rare in cats. Most arise spontaneously without a known cause. When they occur, bone tumors are typically aggressive in dogs but less so in cats depending on the specific tumor type. Bone tumors may affect the long bones of the limbs or the bones of the spine, pelvis, ribs, or skull.

Large and giant breed dogs are more commonly affected, though small dogs can develop bone tumors as well. While older dogs and cats are most frequently diagnosed, younger dogs are also at risk for primary bone tumors.

If your pet develops a persistent limp, swelling over a bone, or pain that does not improve, it is important to have them evaluated by a veterinarian. Many causes of lameness are not cancer. However, bone cancer, including osteosarcoma, should be considered when limping is persistent, painful, or worsening. Early diagnosis can help relieve pain, determine the cause, and provide the best treatment options.

What Are Primary Bone Tumors?

Primary bone tumors arise from the cells that make up bone. These tumors are different from cancers that spread (metastasize) to bone from another location in the body. The most common bone tumor in dogs and cats is osteosarcoma. Other primary bone tumors include chondrosarcoma, hemangiosarcoma, fibrosarcoma, and multilobular osteochondrosarcoma (MLO). Osteosarcoma most commonly affects the long bones of the legs in both dogs and cats, however, it can originate from any bone in the body.

What Are the Signs of Bone Cancer in Dogs and Cats?

Many pet owners first notice bone cancer because of changes in their pet’s mobility, comfort, or activity level. In dogs, osteosarcoma often develops in the limbs and may initially appear as a minor limp that gradually worsens.

The signs of a primary bone tumor often develop gradually but typically worsen over time. Depending on the location of the tumor, pets may experience:

• Persistent limping or lameness

• Swelling over an affected bone

• Pain or sensitivity when the area is touched

• Reluctance to run, jump, or exercise

• Decreased activity or lethargy

• Loss of appetite in some cases

• A sudden fracture after minor trauma (called a pathologic fracture)

These signs can also occur with injuries, arthritis, or other orthopedic conditions, making a veterinary examination essential for an accurate diagnosis.

Diagnosing Primary Bone Tumors

Your veterinarian will perform a physical examination and obtain a complete medical history. Radiographs (X-rays) are typically the first diagnostic step and may reveal changes suggestive of a bone tumor.

If imaging findings are concerning for bone cancer, your veterinarian may recommend additional testing, such as fine needle aspiration or biopsy, to confirm the diagnosis and identify the specific type of tumor. Blood work may also be recommended to evaluate your pet’s overall health before treatment.

Your veterinarian may also refer your pet to a veterinary oncologist, who can help recommend the next diagnostic steps, explain treatment options, and coordinate care with your primary veterinarian.

Once a bone tumor is suspected or confirmed, staging tests may be recommended to determine whether cancer has spread to other areas of the body. Depending on your pet’s situation, this may include chest radiographs (X-rays), CT imaging, or other advanced diagnostics.

These results help your veterinary team recommend treatment options that fit your pet’s diagnosis, comfort, and overall health.

Treating Primary Bone Tumors

Treatment recommendations depend on the tumor type, location, whether cancer has spread, and your pet’s overall health.

For pets diagnosed with osteosarcoma or another type of bone cancer, treatment typically focuses on controlling pain, preserving mobility, and maintaining quality of life. Your veterinary surgeon and oncology team will work with you to determine the most appropriate approach for your pet.

Surgery is often recommended, particularly amputation for tumors affecting the limbs. While the thought of amputation can be difficult for many families, most dogs adapt remarkably well and experience significant pain relief after surgery.

In select cases, limb-sparing surgery may be an alternative to amputation. This procedure removes the portion of bone affected by the tumor while preserving the limb. Limb-sparing surgery is not appropriate for every pet and depends on factors such as the tumor’s location, size, and your pet’s overall health. Your veterinary surgeon can determine whether this approach is an option for your pet.

Radiation therapy may also be used as a primary treatment, such as stereotactic radiation therapy, or as palliative care to help relieve pain from a primary bone tumor. 

Chemotherapy is commonly recommended for dogs with osteosarcoma. Its goal is to target microscopic metastatic cancer cells, and it has been shown to improve prognosis beyond surgery or radiation therapy alone.

For some pets with complex cancers, additional advanced treatment options may also be considered. For example, some dogs with osteosarcoma may qualify for an immunotherapy protocol that uses apheresis to collect specific white blood cells for processing. Because eligibility and timing are important, families should ask their veterinarian about this option before amputation.

Every treatment plan is individualized. Your veterinary oncologist, primary veterinarian, and veterinary surgeon will discuss the benefits, risks, expected outcomes, and your pet’s quality of life when recommending treatment options.

Quality of Life and Prognosis After Treatment

Many pets can continue to have a good quality of life following treatment for bone cancer. Dogs often adapt very well after limb amputation and can return to many of the activities they enjoyed before surgery.

The prognosis depends on the specific type of tumor, whether cancer has spread, and the treatment selected. Osteosarcoma in dogs is an aggressive form of bone cancer with a high likelihood of spreading, which is why early evaluation, staging, and treatment planning are important. Treatment can often provide meaningful pain relief and help dogs maintain good quality time with their families.

Cats with osteosarcoma generally have a more favorable prognosis because the disease is less likely to metastasize.

If your veterinarian is concerned about bone cancer, MedVet’s board-certified medical oncologists and radiation oncologists can help evaluate your pet and recommend the next steps.

MedVet is a nationwide network of emergency and specialty hospitals founded, owned, and led by veterinarians. Our teams provide 24/7 emergency care alongside a wide range of specialty services, with board-certified specialists collaborating across disciplines to deliver advanced, compassionate care for pets and the people who love them.

Find a MedVet location near you.