Osteosarcoma (OSA) is the most common primary bone tumor in dogs. OSA accounts for roughly 5 percent of all canine tumors. It's a malignant bone tumor which can develop in any bone. While it typically occurs in bones bordering the wrist, knee and shoulder, it may also impact the cranium, spinal column and ribs. Osteosarcoma of the limbs -- appendicular osteosarcoma -- accounts for 75-85 percent of bone cancer cases. If your pet has osteosarcoma, you do have options. This concise book outlines the causes, available tests and treatment options for the disease.