I've said this a few times and there are a few other people who've had similar situations (one had long term irritation from braces and discovered only post removal of the braces that she actually had scc). Mine was similar as it started out with a broken tooth irritating an area - I had built up a small callous under my tongue suppose to protect against the tooth - an oral surgeon removed it (the callous was biopsied and came back as thickened skin). After it seemed okay for a while as I had the tooth capped. Then long term the irritation began in earnest I had a biopsy but at the time my tongue had no sore - it was only irritated - however palpation of the area would have shown a small lump inside my tongue - I assumed this was scar tissue from where they'd removed the callous a few years previously. The ENT said nothing biopsy came back irritated and inflamed skin. I had the tooth filed, allergy tests etc.. No result. Jump ahead 2 years - i had the tooth beside the other capped and the situation became worse the ENT biopsied it - scc.
Some drs believe there is an association between long term irritation and scc - some don't. The truth is long term irritation causes cell change (this is what happens in the tissue of the lungs, and oral mucosa when exposed to chemicals from cigarette smoking - from which we often get cancer), so I think the same holds true for other types of irritation - whether it be mechanical or chemical. Take care.