A white oral lesion that CANNOT be wiped off should suggest all of the following EXCEPT:

Pseudomembranous candidiasis (thrush) is the classic white lesion that CAN be wiped off, leaving an erythematous base; the others (leukoplakia, lichen planus, frictional keratosis) are adherent and do not rub off.Other options: Leukoplakia, lichen planus, and frictional keratosis are non-removable white lesions.Key exam takeaway: Thrush wipes off; leukoplakia, lichen planus, and keratoses do not.