Margaret,
I dont have many answers for you, but I can tell you this. My dad had his 2nd PET a few weeks ago, and it came back clean. His onc. sent him to a surgeon, who told him that a PET isnt "for sure" and wanted more tests. (A CT and biopsy). My dad nearly jumped out of his skin. He was so sure he was gonna have surgery and the PET was right. They gave him a CT and the biopsy, and everything did come back clean. It seems the PET was right all along. Im not saying that it is true in ALL cases, but in ours, the PET was right from the beginning. I know though, it is more likley for a PET to give a false negative then a false positive. Although it does happen. Get a second opinion, and do the necessary tests. I hope the best for you.
Jamie