The giant breeds at greatest risk for developing osteosarcoma include Great Danes, St. Bernards, Great Pyrenees, Newfoundlands, Bernese Mountain Dogs, and Irish Wolfhounds. Large breeds such as Rottweillers, Labradors, Golden Retrievers, Shepherds, Dobermans, Weimaraners and Boxers are also at an increased risk. It is not a very common tumor in small breed dogs and rarely occurs in cats. Dogs that weigh over 80 pounds have been shown to be at least 60 times more likely to develop an osteosarcoma than dogs weighing less than 75 pounds. While older dogs more commonly develop osteosarcomas, there does appear to be an increased incidence in one to two year old dogs as well.
Male dogs have an increased incidence of osteosarcomas.
It is unknown why some dogs develop osteosarcomas, but one theory suggests that the rapidly growing cells found at the growth plates in the bones are genetically at a greater risk of mutation. Another theory is that the tumors develop at the site of trauma. The increased cellular activity at the site of a fracture or trauma could result in the development of cancer cells. The reality is that both of these may be true and there may be other causes not yet discovered. The symptoms of osteosarcomas are often closely associated with their location.