The clinical appearance, including the surface texture and color, may be homogeneous or non-homogeneous (see: classification). Some signs are generally associated with a higher risk of cancerous changes (see: prognosis). Leukoplakia may rarely be associated with esophageal carcinoma. : 805

Causes
The exact underlying cause of leukoplakia is largely unknown, but it is likely multifactorial, with the main factor being the use of tobacco. Tobacco use and other suggested causes are discussed below. The mechanism of the white appearance is thickening of the keratin layer, called hyperkeratosis. The abnormal keratin appears white when it becomes hydrated by saliva, and light reflects off the surface evenly. This hides the normal pink-red color of mucosae (the result of underlying vasculature showing through the epithelium). A similar situation can be seen on areas of thick skin such as the soles of the feet or the fingers after prolonged immersion in water. Another possible mechanism is thickening of the stratum spinosum, called acanthosis. Tobacco
Tobacco smoking or chewing is the most common causative factor, with more than 80% of persons with leukoplakia having a positive smoking history. Smokers are much more likely to develop leukoplakia than non-smokers. The size and number of leukoplakia lesions in an individual is also correlated with the level of smoking and how long the habit has lasted for. Other sources argue that there is no evidence for a direct causative link between smoking and oral leukoplakia. Cigarette smoking may produce a diffuse leukoplakia of the buccal mucosa, lips, tongue and rarely the floor of mouth.
The surface texture is irregular compared to homogeneous leukoplakia, and may be flat (papular), nodular or exophytic. "Verrucous leukoplakia" (or "verruciform leukoplakia") is a descriptive term used for thick, white, papillary lesions. Verrucous leukoplakias are usually heavily keratinized and are often seen in elderly people. Some verrucous leukoplakias may have an exophytic growth pattern, and some may slowly invade surrounding mucosa, when the term proliferative verrucous leukoplakia may be used. Non-homogeneous leukoplakias have a greater risk of cancerous changes than homogeneous leukoplakias. Proliferative verrucous leukoplakia
Proliferative verrucous leukoplakia (PVL) is a recognized high risk subtype of non-homogeneous leukoplakia. It is uncommon, and usually involves the buccal mucosa and the gingiva (the gums). This condition is characterized by (usually) extensive, papillary or verrucoid keratotic plaques that tends to slowly enlarge into adjacent mucosal sites. An established PVL lesion is usually thick and exophytic (prominent), but initially it may be flat. Smoking does not seem to be as strongly related as it is to leukoplakia generally, and another dissimilarity is the preponderance for women over 50. There is a very high risk of dysplasia, transformation to squamous cell carcinoma with high mortality (PVL does not transform into verrucous carcinoma, which is a lesion with a good prognosis usually; the similarity of names does not reflect the common origin, but only the resemblance of their appearance). Erythroleukoplakia
Erythroleukoplakia (also termed speckled leukoplakia, erythroleukoplasia or leukoerythroplasia) is a non-homogeneous lesion of mixed white (keratotic) and red (atrophic) color.