lower labial mucosa. Leukoplakia of the floor of the mouth and tongue accounts for over 90% of leukoplakias showing dysplasia or carcinoma on biopsy. This is thought to be due to pooling of saliva in the lower part of the mouth, exposing these areas to more carcinogens held in suspension. Red lesions (erythroplasia) and mixed red and white lesions (erythroleukoplakia/"speckled leukoplakia") have a higher risk of malignant change than homogeneous leukoplakia. Verrucous or nodular areas have a higher risk. Although smoking increases risk of malignant transformation, smoking also causes many white patches with no dysplasia. This means that statistically, white patches in non-smokers have a higher risk. Older people with white patches are at higher risk. Larger white patches are more likely to undergo malignant transformation than smaller lesions. White patches which have been present for a long period of time have a higher risk. Persons with a positive family history of cancer in the mouth. Candida infection in the presence of dysplasia has a small increased risk. A change in the appearance of the white patch, apart from a change in the color, has a higher risk. Changes in the lesion such as becoming fixed to underlying tissues, ulceration, cervical lymphadenopathy (enlargement of lymph nodes in the neck), and bone destruction may herald the appearance of malignancy. White patches present in combination with other conditions that carry a higher risk (e.g. oral submucous fibrosis), are more likely to turn malignant. Although overall, oral cancer is more common in males, females with white patches are at higher risk than men. Epidemiology The prevalence of oral leukoplakia varies around the world, but generally speaking it is not an uncommon condition. Reported prevalence estimates range from less than 1% to more than 5% in the general population. Leukoplakia is, therefore, the most common premalignant lesion that occurs in the mouth. Leukoplakia is more common in middle-aged and elderly males. The prevalence increases with increasing age. In areas of the world where smokeless tobacco use is common, there is a higher prevalence. In the Middle East region, the prevalence of leukoplakia is less than 1% (0.48%). Etymology The word leukoplakia means "white patch", and is derived from the Greek words λευκός - "white" and πλάξ - "plate". History The term leukoplakia was coined in 1861 by Karl Freiherr von Rokitansky, who used it to refer to white lesions of the urinary tract. In