Osteosarcoma is an aggressive malignant tumor arising from primitive transformed cells of the connective tissue of bones. It is the most common form of bone cancer. Although it can affect any breed of dog, but is more commonly found in the larger breeds. It is most commonly seen at the end of long bones. The condition is extremely aggressive and has a tendency to rapidly metastasize.
Symptoms are usually subtle. They can include swelling, lameness, and joint or bone pain, lethargy and anorexia. Sometimes a mass or growth or a painful inflammation around the sight of the tumor can be observed.