However, it is possible that some cases had gross metastatic disease that was not detected by the baseline staging tests, that included three view thoracic radiographs in all cases but not all for abdominal ultrasound and thoracic/abdominal CT scan, and therefore, some of the elevated baseline serum uPA/uPAR levels may not accurately represent the profiles of dogs with appendicular osteosarcoma without gross metastatic disease. This evidence concerns the gene PLAU and metastatic neoplasm.