Osteosarcoma is a type of tumor that forms in the bones of a dog, most often affecting the limbs. These tumors develop on the inner portion of the bone, and as they grow, slowly cause the bone to "explode" from the inside out. Osteosarcoma is an extremely aggressive and painful form of cancer in dogs. Accordingly, dogs who are having issues with lameness or pain should be taken to a veterinarian immediately to rule out the possibility of osteosarcoma.
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Osteosarcoma Facts
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Osteosarcoma makes up nearly 90 percent of all cancerous tumors affecting the bone. However, it only accounts for approximately 5 percent of all tumors in dogs, tending to primarily affect older and larger dogs, such as Great Danes, Saint Bernards, Rottweilers and Golden Retrievers.
Symptoms
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Most cases of osteosarcoma develop on one of the legs, usually below the joint. Tumors can grow near the growth plates, and there may also be swelling, pain and lameness of the affected leg. Unfortunately, osteosarcoma often spreads easily, and up to 90 percent of all cases include cancerous cells that have moved into the lungs by the time of diagnosis.
Causes
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The true cause of osteosarcoma is unknown, but there may be a variety of factors contributing to its development. Osteosarcoma tumors are most often found near growth plates. Some veterinarians speculate that excessive or abnormal growth causes the condition and that there may be potential added risk if the bone has been damaged previously. As with humans, it is speculated that osteosarcoma can also be due to carcinogens, foreign materials, radiation, metal implants, bullets and transplants of bone or tissue. Also, it appears that certain larger breeds of dogs are prone to developing osteosarcoma, which may signal that the disease can be hereditary.
Diagnosis
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When a dog sees a veterinarian for lameness, swelling or any of the above-mentioned symptoms, the area is often X-rayed. For most dogs, this is enough to diagnosis osteosarcoma. In some cases, the diagnosis may be unclear. In this case, the veterinarian may perform a biopsy on a small section of the bone to gain an absolutely positive diagnosis of osteosarcoma.
Treatment
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Treating osteosarcoma involves taking aggressive action against the cancer. If it has been identified in one of the legs, it is often amputated. This does not necessarily stop the spread but will provide absolute pain relief to the dog. In very rare cases the dog may have his leg spared, but this is usually not the case due to the inner bone growth patterns of osteosarcoma.
Following amputation of the affected leg, a dog suffering from osteosarcoma will undergo chemotherapy. Medications such as carboplatin and cisplatin are administered and have had positive results.
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