Canine Osteosarcoma on the Skull

Canine osteosarcoma (OSA) is a nasty disease that accounts for 80 percent of malignant bone cancers in dogs, according to the College of Veterinary Medicine (CVM) at the University of Georgia. The disease is classified as a rapidly growing and destructive neoplasm, which is a new and abnormal growth of tissue, of the bone. OSA effects dogs more than any other mammal on the planet. OSA of the skull is called axial OSA and is less common.

  1. Causes and Development

    • Exposure to chemical carcinogens, pre-existing skeletal deformities; such as healed fractures, and internal foreign bodies like metal plates are known to directly influence the growth of OSA tumors. Furthermore, tumor development is synchronous with genetic predisposition in certain family-lines. DNA viruses like polyomavirus and SV-40 virus and RNA viruses like type C retroviruses are known to induce OSA tumors. 90 percent of large and giant dog breeds are more likely to develop OSA, according to the CVM. The disease usually develops when a dog reaches an age around 7.5 years. OSA is slightly more common in male dogs -- and is quite rare in small dog breeds.

    Sites of Origin

    • The most common form of OSA is appendicular. Appendicular OSA originates along the forelimbs, which are responsible for carrying the brunt of a dog's weight throughout its life. The more rare axial OSA involves the vertebrae, ribs and skull. OSA of the skull originate in the cranial vault, zygomatic arch and the jaw. In rare cases, OSA of the skull will originate in the nasal cavity. Moreover when OSA originates in the skull, it's often multilobular which means several clearly defined tumors grow at once. Axial OSA is more common in female dogs than male dogs and usually develops in middle-aged animals.

    Clinical Signs and Symptoms

    • Axial OSA originating in the skull can cause neurological deficits and severe nose bleeds. Furthermore, dogs with skull OSA will develop tumors that are clearly visible with the naked eye. Sluggish behavior, aggression and irritability are also potential symptoms.

    Treatment

    • Treatment varies from chemotherapy, surgery and radiation. If a dog goes untreated it likely only has 2 to 6 months of life left. In some instances amputation helps, but often just temporarily slows the disease. If the amputation proves successful chemotherapy is induced to increase survival time. Even though amputation rarely works it's the dogs best chance at a longer life. Dogs between ages 7 and 10 will have better odds at surviving longer than younger and older dogs with OSA