Same for me. I had an unknown primary and a ct and pet were ordered. They were done from the waist up. All clean. But a byopsy was done on the lump on my neck and it was cancerous. I had a procedure and the doctor found the primary on the tonsil and removed most of it. I then underwent a radical neck disection left side to get it all. After that, I did radiation (33). He never really explained why nothing showed on the PET and CT. Maybe he expected it. But I believe from what I read, PET is more accurate. Maybe just not in the head and neck area. Wish you well.

Jeff