Osteosarcoma of the patella with pulmonary metastases in a dog

A 6-year-old neutered male Rottweiler was examined for a progressive right pelvic limb lameness. In radiographs of the right stifle, there was an oste olytic lesion with irregular new bone formation along the cranial aspect of the patella consistent with an aggressive bone lesion. In thoracic radiogr aphs, there were multiple soft tissue nodular opacities throughout the lung fields, consistent with pulmonary metastases. Microscopically, fine needle aspirate samples from the right patella contained pleomorphic spindle cell s with cytologic features of osteosarcoma. The presence of pulmonary metast ases at the time of initial diagnosis in the dog described herein suggests that osteosarcoma of the patella has tile potential for similar aggressive biologic behavior as that seen in dogs with appendicular osteosarcoma.