My whippet Rickie had this cancer on his upper right rear leg. Regular vet removed it, didn't get clean margins. It came back a year later - I found it very early as I was checking the site regularly. Specialty clinic surgeon removed it this time (very aggressive surgery), got clean margins by millimeters, and we haven't had a recurrence. Rickie was 10 at the time of the second surgery. He will be 14 tomorrow. Based on this experience I would recommend checking the site regularly for any sign of a return, however small, so that you can take action right away. As others have said, it doesn't always come back, and I hope Kato's won't.