• Appendicular osteosarcoma is the most common form of primary bone cáncer in dogs that primarily affects middle-aged to older dogs of large and giant breeds • The typical presentation includes a progressive lameness with a radiographic lesion of the metaphysis of the distal radius or proximal humerus, with the distal femur and proximal or distal tibia also being affected • Initial work up can involve either bone aspirate for cytology or bone biopsy • Staging tests should involve evaluation of the lungs and other bone sites • The standard therapy for this disease is amputation followed by systemic chemotherapy • Median survival time for this disease is 10 months