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Malignant bone tumors in the dog
Last reviewed: 04.07.2025
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Bone tumors can be malignant or benign. Osteosarcoma and chondrosarcoma are the two most malignant bone tumors. Osteomas and osteochondromas are benign.
Osteosarcoma is the most malignant type of bone cancer in dogs. It affects dogs of all ages, with the average age of dogs with osteosarcoma being 8 years. This cancer affects males and females equally. Large breeds such as St. Bernards, Newfoundlands, Great Danes, and Great Pyrenees are 60 times more likely to develop osteosarcoma than dogs weighing less than 22 pounds. Large dogs such as Irish Setters and Boxers are 8 times more likely to develop osteosarcoma. Small dogs are rarely affected by this cancer.
Osteosarcoma most commonly occurs in the front legs, followed by the hind legs, flat bones of the ribs, and lower jaw. The most common first sign is lameness in a mature dog with no history of trauma. It is usually ignored until swelling of the limb occurs. Pressure on the tumor causes pain. Fractures may occur at the site of the tumor.
X-ray examination may suggest the disease, but a precise diagnosis depends on a tumor biopsy. Osteosarcoma is an aggressive cancer that spreads rapidly into tumors.
Chondrosarcoma is the second most common malignant bone tumor in dogs. The average age of onset is 6 years. This tumor often affects the ribs, nasal bones, and pelvic bones. It presents as a large, firm, painless swelling where there is cartilage. This tumor also metastasizes to the lungs, but not as aggressively as osteosarcoma.
Treatment: Malignant tumors such as osteosarcomas and chondrosarcomas should be treated aggressively. Because these tumors metastasize to the lungs, it is important to perform chest radiographs prior to surgical treatment. The dog should have a complete physical examination, including a complete blood count and fine-needle aspiration biopsy of any enlarged lymph nodes.
The only effective treatment for osteosarcoma of the limb is partial or total amputation. Most dogs do well on three legs. Although amputation rarely cures the cancer, it does relieve pain and improve the dog's quality of life. It should be done at least one joint above the affected bone. Some veterinary centers are using new surgical techniques that allow the limb to be saved.
Chemotherapy in addition to amputation increases the survival rate of dogs with osteosarcoma, but does not improve the cure rate. If the cancer has already metastasized or is at an advanced stage, radiation therapy may be considered, but this is also not curative. Osteosarcoma of the mandible is treated with radiation, to which it is moderately sensitive. Radiation is also used to relieve pain.
Complete surgical removal of chondrosarcoma provides relief, but should not be considered curative.
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