The flex scope can see the top of the bot, but the BOT also has deep musculature that can't be seen, and that makes the BOT more difficult to treat if it is cancer. HPV related does not have the typical signs like tobacco related cancer does, and often has no signs or symtoms of cancer until it's advanced, and often the first sign is from a swollen lymph node. I had three office flex scopes that nothing could be seen from, however, they knew there was cancer from the lymph node FNAB. A triple scope, under anesthesea, with biopsy, found the tonsil was the source.