Osteosarcoma is a painful and aggressive bone tumor in dogs that is known to be more common in certain breeds than others. New research has now confirmed that larger breeds, such as Rottweiler, Great Dane and Rhodesian Ridgeback, have a greater risk of osteosarcoma than smaller breeds, as well as showing that breeds with shorter skulls and legs have lower osteosarcoma risk. The findings could inform future breed health reforms as well as studies into the way tumors develop from normal bone.