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Chondrosarcoma of the Bone in Dogs

Chondrosarcoma (CSA) of the bone is a fast spreading and malignant form of cancer, which, if not diagnosed and treated early, can be life threatening. Chondrosarcoma arises from the cartilage of the body, the connective tissue that is found between the bones and joints, often metastasizing to other parts of the body, including the ribs. This is the most common rib tumor found in dogs, and the second most common primary tumor in dogs, representing 5 to 10 percent of all primary bone tumors.

The majority of CSAs involves flat bones, with about 30 percent occurring in the nasal cavity and about 20 percent involving the ribs. This form of cancer also affects the limbs, with a resulting weakening in the structure of the bone due to the invasive tumor. Fractures of the bone are common.

Large dog breeds are at higher risk, as well as older dogs. Chondrosarcoma most commonly affects dogs around eight years of age, but it has been found in dogs of almost all ages.

Symptoms and Types

• If tumor is affecting leg, lameness will be observed
• Pain in affected area, e.g. limb
• Swelling at tumor site
• Sneezing and difficult breathing if tumor involves nasal cavity
• Nasal discharge and/or nose bleed if tumor involves nasal cavity
• Fracture in the bone of the affected limb
• Other signs will depend upon the metastatic site(s)

Causes

Although an exact cause has not been identified, multiple cartilaginous growths or protuberance may lead to this form of cancer.

Diagnosis

You will need to give a thorough history of your dog’s health and onset of symptoms. Your veterinarian will perform a thorough physical exam on your dog, including a complete blood count (CBC), a biochemistry profile, and a urinalysis. The results of these tests are usually within normal ranges. Tissue samples from the local lymph nodes will also be taken for analysis of cancer cells and evidence of immune system response.

Radiographic studies of the affected areas may show the extent of the tumor’s invasion. X-rays, computed tomography (CT) scans, nuclear bone scans, and radiographic scans will usually be helpful in diagnosing the stage and type of the tumor. Bone scans may show involvement of soft tissue and adjacent bones. The most conclusive and direct method for making a diagnosis is normally by taking a biopsy of the growth for microscopic laboratory analysis.