Except when the ENT says something like -"now thanks not at all what I expected !"

Yes they can occur anywhere, however, I seem to recall my ENT telling me after completing my first treatments that oral cancers in younger people do tend to reoccur and "reoccur with a vengeance" between 15 to 20 years after the first. He didn't have any concrete evidence or studies, it was just from his personal experience. The second diagnosis may be a result from the initial treatment......again, he was speaking from his experience only. We were told to watch the same site in the mouth, brain, throat and lungs in particular.

(I really hated proving him right)

Good Luck