Leukoplakia is a clinical term only and refers to a mucosal white plaque that does not represent any other known clinical or histopathologic entity; it is therefore a clinical diagnosis of exclusion. Frictional keratoses have a specific etiology and are therefore not considered to be leukoplakias. Leukoplakia is a common oral finding that can be a precursor of mucosal squamous cell carcinoma. It is more common in smokers, but that may be because white plaques in smokers tend to be biopsied more frequently. The risk factors for this condition are the same as those for squamous cell carcinoma, and malignant transformation to invasive carcinoma occurs in 6%-18% of patients.

All leukoplakias represent one of the following:

1. Epithelial dysplasia, carcinoma in situ, or invasive carcinoma
2. Hyperkeratosis of unknown etiology

In the older literature, the prevalence of dysplasia, carcinoma in situ, or invasive carcinoma (usually squamous cell carcinoma) was 10%-20%. However, more recent data suggest that this may be as high as 40%.

Leukoplakia is most commonly found in middle-aged or elderly men. Leukoplakia in women can also involve the vulva, usually in obese postmenopausal females.