User:Ian Furst/Dysplasia (mouth)

User:Ian Furst/leukoplakia User:Ian Furst/leukoplakia sign

• Classification: If relevant. May also be placed as a subheading of diagnosis
• Signs and symptoms or Characteristics

Etiology|Causes

: Includes Risk factors, triggers, Genetics or genome, Virology (e.g., structure/Morphology, replication). 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 suffer from 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. Reverse smoking, where the lit end of the cigarette is held in the mouth is also associated with mucosal changes. Tobacco chewing, e.g. betel leaf and areca nut, called paan, tends to produce a distinctive white patch in a buccal sulcus termed "tobacco pouch keratosis". In the majority of persons, cessation triggers shrinkage or disappearance of the lesion, usually within the first year after stopping.

Alcohol

Although the synergistic effect of alcohol with smoking in the development of oral cancer is beyond doubt, there is no clear evidence that alcohol is involved in the development of leukoplakia, but it does appear to have some influence. Excessive use of a high alcohol containing mouth wash (> 25%) may cause a grey plaque to form on the buccal mucosa, but these lesions are not considered true leukoplakia.

Sanguinaria

Sanguinaria (Bloodroot) is a herbal extract which is included in some toothpastes and mouthwashes. Its use is strongly associated with development of leukoplakia, usually in the buccal sulcus. This type of leukoplakia has been termed "sanguinaria associated keratosis" and more than 80% of people with leukoplakia in the vestibule of the mouth have used this substance. Upon stopping contact with the causative substance, the lesions may persist for years. Although this type of leukoplakia may show dysplasia, the potential for malignant transformation is unknown.

Ultraviolet radiation

Ultraviolet radiation is believed to be a factor in the development of some leukoplakia lesions of the lower lip, where there is usually, additionally, an association with actinic cheilosis.

Micro-organisms

Candida in its pathogenic hyphal form is occasionally seen in biopsies of idiopathic leukoplakia. It is debated whether candida infection is a primary cause of leukoplakia with or without dysplasia, or a superimposed (secondary) infection that occurs after the development of the lesion. It is known that Candida species thrive in altered tissues. Some leukoplakias with dysplasia reduce or disappear entirely following use of antifungal medication. Smoking, which as discussed above can lead to the development of leukoplakia, can also promote oral candidiasis. Candida in association with leukoplakia should not be confused with white patches which are primarily caused by candida infection, such as chronic hyperplastic candidiasis ("candidal leukoplakia").

The involvement of viruses in the formation of some oral white lesions is well established, e.g. Epstein-Barr virus in oral hairy leukoplakia (which is not a true leukoplakia). Human papilloma virus (HPV), especially HPV 16 and 18, is sometimes found in areas of leukoplakia, however since this virus can be coincidentally found on normal, healthy mucosal surfaces in the mouth, it is unknown if this virus is involved in the development of some leukoplakias. In vitro experimentation has demonstrated that HPV 16 is capable of inducing dysplastic changes in previously normal squamous epithelium.

Epithelial atrophy

Leukoplakia is more likely to develop in areas of epithelial atrophy. Conditions associated with mucosal atrophy include iron deficiency, some vitamin deficiencies, oral submucous fibrosis, syphilis and sideropenic dysphagia.

Tumor suppressor genes - p53

Tumor suppressor genes are genes involved in the regulation of normal cell turnover and apoptosis (programmed cell death). One of the most studied tumor suppressor genes is p53, which is found on the short arm of chromosome 7. Mutation of p53 can disrupt its regulatory function and lead to uncontrolled cell growth. Mutations of p53 have been demonstrated in the cells from areas of some leukoplakias, especially those with dysplasia and in individuals who smoke and drink heavily.

Trauma

Another very common cause of white patches in the mouth is frictional or irritational trauma leading to keratosis. Examples include nicotine stomatitis, which is keratosis in response to heat from tobacco smoking (rather than a response to the carcinogens in tobacco smoke). The risk of malignant transformation is similar to normal mucosa. Mechanical trauma, e.g. caused by a sharp edge on a denture, or a broken tooth, may cause white patches which appear very similar to leukoplakia. However, these white patches represent a normal hyperkeratotic reaction, similar to a callus on the skin, and will resolve when the cause is removed. Where there is a demonstrable cause such as mechanical or thermal trauma, the term idiopathic leukoplakia should not be used.

• Pathophysiology or Mechanism

Diagnosis: Includes characteristic biopsy findings and differential diagnosis.

NEED DISCUSSION OF DIAGNOSTIC TOOLS, BLUE LIGHT, ETC...

Histologic appearance

Leukoplakia has a wide range of possible histologic appearances. The degree of hyperkeratosis, epithelial thickness (acanthosis/atrohpy), dysplasia and inflammatory cell infiltration in the underlying lamina propria are variable. In mucous membranes, hyperkeratosis can be defined as "an increase in the thickness of the keratin layer of the epithelium, or the presence of such a layer in a site where none would normally be expected." In leukoplakia, the hyperkeratosis varies in thickness, and may be either ortho- or para-keratosis, (depending upon whether cell nuclei are lost or retained in the superficial layers respectively), or a mixture of both in different areas of the lesion.

The epithelium may show hypertrophy (e.g. acanthosis) or atrophy. Red areas within leukoplakia represent atrophic or immature epithelium which has lost the ability to keratinize. The transition between the lesion and normal surrounding mucosa may be well demarcated, or poorly defined. Melanin, a pigment naturally produced in oral mucosa, can leak from cells and give a grey color to some leukoplakia lesions.

Hyperkeratosis and altered epithelial thickness may be the only histologic features of a leukoplakia lesion, but some show dysplasia. The word dyspalsia generally means "abnormal growth", and specifically in the context of oral red or white lesions refers to microscopic changes ("cellular atypia") in the mucosa that indicate a risk of malignant transformation. When dysplasia is present, there is generally an inflammatory cell infiltration in the lamina propria. The following are commonly cited as being possible features of epithelial dysplasia in leukoplakia specimens:

• Cellular pleomorphism, in which cells are of abnormal and different shapes.
• Nuclear atypia, in which the nuclei of cells varies in size, any may be increased in size relative to the cytoplasm, shape, and may stain more intensely. There may also be more prominent nucleoli.
• Increased number of cells seen undergoing mitosis, including both normal and abnormal mitoses. Abnormal mitosis may be abnormally located, e.g. occurring in suprabasal cells (cell layers more superficial to the basal cell layer) or of abnormal form, e.g. "tri-radiate mitoses" (a cell splitting into 3 daughter cells rather than only 2)
• Loss the normal organization of the epithelial layers. The distinction between the epithelial layers may be lost. Normally stratified squamous epithelium shows progressive changes in the form of cells from the basal to the superficial layers, with cells becoming more flat ("squames") towards the surface as a continuous maturation process. In dysplastic epithelium, cells may become vertically orientated rather than becoming flat towards the surface.
• There may be abnormal keratinization, where keratin is formed below the normal keratin layer. This can occur in individual cells or groups of cells, forming an intraepithelial keratin pearl. There may be an increase in number of basal cells, and they may lose their cellular orientation (losing their polarity and long axis).
• Alteration of the normal epithelial-connective tissue architecture - the rete pegs may become "drop shaped". wider at their base than more superficially.

Generally dysplasia is subjectively graded by pathologists into mild, moderate or severe dysplasia. This requires experience as it is a difficult skill to learn. It has been shown that there is high degree of inter-observer variation and poor reproducibility in how dysplasia is graded. Severe dysplasia is synonymous with the term carcinoma in situ, denoting the presence of neoplastic cells which have not yet penetrated the basement membrane and invaded other tissues.

• Prevention or Screening (if the section only discusses secondary prevention it should follow the treatment section)

Treatment

A systematic review found that no treatments commonly used for leukoplakia have been shown to be effective in preventing malignant transformation. Some treatments may lead to healing of leukoplakia, but do not prevent relapse of the lesion or maliginant change. Regardless of the treatment used, a diagnosis of leukoplakia almost always leads to a recommendation that possible causative factors such as smoking and alcohol consumption be stopped, and also involves long term review of the lesion, to detect any malignant change early and thereby improve the prognosis significantly.

Removal of possible predisposing factors and review

Beyond advising smoking cessation, many clinicians will employ watchful waiting rather than intervene. Recommended recall intervals vary. One suggested program is every 3 months initially, and if there is no change in the lesion, then annual recall thereafter. Some clinicians use clinical photographs of the lesion to help demonstrate any changes between visits. Watchful waiting does not rule out the possibility of repeated biopsies. If the lesion changes in appearance repeat biopsies are especially indicated. Since smoking and alcohol consumption also places individuals at higher risk of tumors occurring in the respiratory tract and pharynx, "red flag" symptoms (e.g. hemoptysis - coughing blood) often trigger medical investigation by other specialties.

Surgical removal

Surgical removal of the lesion is the first choice of treatment for many clinicians. However, the efficacy of this treatment modality cannot be assessed due to insufficient available evidence. This can be carried out by traditional surgical excision with a scalpel, with lasers, or with eletrocoutery or cryotherapy. Often if biopsy demonstrates moderate or severe dysplasia then the decision to excise them is taken more readily. Sometimes white patches are too large to remove completely and instead they are monitored closely. Even if the lesion is completely removed, long term review is still usually indicated since leukoplakia can recur, especially if predisposing factors such as smoking are not stopped.

Medications

Many different topical and systemic medications have been studied, including anti-inflammatories, antimycotics (target Candida species), carotenoids (precursors to vitamin A, e.g. beta carotene), retinoids (drugs similar to vitamin A), and cytotoxics, but none have evidence that they prevent malignant transformation in an area of leukoplakia. Vitamins C and E have also been studied with regards a therapy for leukoplakia. Some of this research is carried out based upon the hypothesis that antioxidant nutrients, vitamins and cell growth suppressor proteins (e.g. p53) are antagonistic to oncogenesis. High doses of retinoids may cause toxic effects. Other treatments that have been studied include photodynamic therapy.

Prognosis

The annual malignant transformation rate or leukoplakia rarely exceeds 1%, i.e. the vast majority of oral leukoplakia lesions will remain benign. A number of clinical and histopathologic features are associated with varying degrees of increased risk of malignant transformation, although other sources argue that there are no universally accepted and validated factors which can reliably predict malignant change. It is also unpredictable to an extent if an area of leukoplakia will disappear, shrink or remain stable.

• Presence and degree of dysplasia (mild, moderate or severe/carcinoma in situ). Dysplasia is the most important predictor of malignant change, and about 10% of leukoplakia lesions show dysplasia when biopsied.
• Leukoplakia located on the floor of the mouth, the posterior and lateral tongue, and the retromolar areas (the region behind the wisdom teeth) have higher risk, whereas white patches in areas such as the top surface of the tongue and the hard palate do not have significant risk. Although these "high risk" sites are recognized, statistically, leukoplakia is more common on the buccal mucosa, alveolar mucosa, and the 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 that homogenous lekuoplakia.
• 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 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

Need to add factors such as incidence, prevalence, age distribution, and sex ratio. 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.

• History: Early discoveries, historical figures, and outdated treatments (not patient history)
• Society and culture: This might include stigma, economics, religious aspects, awareness, legal issues, notable cases
• Research directions: Include only if addressed by significant sources. See Trivia, and avoid useless statements like "More research is needed". Wikipedia is not a directory of clinical trials or researchers.
• Special populations, such as Geriatrics or Pregnancy or Pediatrics
• Other animals