Canine Cancer - Bone Cancer
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| Characteristics / Terms | Hemangiosarcoma | Lymphoma |
| Histiocytomas | Mammary Tumors | Testicular Tumors |
| Mast Cell Tumors | Bone Cancer |
Bone Cancer in Dogs
Bone cancer in dogs can be a challenging disorder to overcome. Bone cancer can occur in any canine. The hallmark of bone cancer (as with all cancers) is uncontrolled cell growth, invasion of cells into nearby structures, and sometimes a dispersal to distant organs, which is termed metastatic cancer. Since any cell in the dog’s body has the potential to develop into a cancerous cell, bone cancer dramatically illustrates what can happen when illness occurs.
When a cell turns cancerous by a disruption of its own physiology, normal neighboring cells usually consume the rogue cell. On other occasions, the defective cell simply self-destructs and is swept away. But in certain circumstances, a modified cell (mutant) makes more cells just like itself. More and more cells arising from that single mutated cell eventually change the environment and carve out their own territory, spreading themselves into more and more neighborhoods. Metastatic bone cancer cells break away and flow to entirely new environments within the dog’s body and begin the malignant process all over again.
Cancer is also termed neoplasia, which means new growth. A cancerous cell grows faster than normal and divides and multiplies at an abnormal rate; its offspring do likewise. From that one abnormal neoplastic cell, more of its kind invade and crowd out surrounding tissues. With bone cancer, there are four types of cell lines capable of evolving into a neoplastic condition:
Osteosarcoma: causing nearly 80% of all bone cancers, this most common form of bone cancer arises from cells that deposit bony minerals. Aggressive invasion and rapid growth make this form of cancer a dreaded threat.
Chondrosarcomas: these tumors arise from the cartilage joint surfaces at the ends of bone and generally have a less aggressive tendency to invade and spread than osteosarcomas.
Fibrosarcomas: originate from fibrous connective tissue adjacent to bone, are locally invasive into the bone, and have a low tendency to spread.
Synovial cell carcinomas: originate from joint tissues and invade the associated bone. These tumors are less aggressive than osteosarcomas.
A definitive diagnosis of bone cancer can only be made via microscopic evaluation of a bone biopsy. Veterinary pathologists classify the degree of malignancy of the cells and likeliness of metastasis to other tissues. Neoplastic cells can be carried by the blood and lymph from the original site of the cancer to distant tissues, at which time a new cancerous growth arises. Called metastatic cancer, whenever distant growths are present in a dog’s body, the magnitude of the ill effects on the patient are remarkably increased, and the chances of a cure drastically reduced.
At-Risk Breeds for Canine Bone Cancer
Most commonly seen in long bones such as the femur, bone cancer has a predilection for larger breeds, including the Greyhound, Saint Bernard, and Mastiff.
Diagnosis
Chronic, low-grade lameness with gradually increasing swelling near a joint alerts the veterinarian to the potential of a tumor. Radiographs of the affected area will display changes in a bone that are totally unlike the defects usually associated with arthritis. On occasion, an apparently normal dog will be presented with a spontaneous lameness. A physical examination, followed by a radiographic evaluation, will reveal the cause of the break to be due to bone cancer. This break is termed a pathological fracture.
Osteosarcoma continues to be one of the most challenging types of cancer to treat. Part of the therapeutic challenge arises from the fact that at the time of diagnosis there often has already been metastasis to other areas of the body.
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