How common is leukoplakia?

Uncommon: But not rare. It is just a thickening of the mucosa due to some type of irritation, whether it be mechanical or chemical.

Pretty common: Leukoplakia means "white patch".This is a fairly common occurrence on the cheeks inside the mouth. There are many causes of leukoplakia, some serious and some not. If the leukoplakia comes and goes, it is probably benign. However, if it remains for a long time, or changes in appearance, this may be an indication of some disease process. See a dentist to have such areas evaluated.