David,

Why are you surprised? There are several people on this board who never smoked and either are not HPV+ or probably weren't based on the location of their tumor (oral tongue instead of tonsils). HPV+ cancers certainly represent a subgroup of oral cancers that can't be explained by smoking but it seems obvious to me they don't explain all of them.

We have an unusual kind of cancer in that the causes can be identified for a large percent of folks who get it but it doesn't surprise me at all that there's also cases which must be caused by factors not yet identified. That's true for almost every other kind of cancer too.

Nelie