be better termed to reflect this etiology, e.g. smokers' keratosis. The second international symposium, therefore, revised the definition of leukoplakia to: "a predominantly white lesion of the oral mucosa that cannot be characterized as any other definable lesion." In the mouth, the current definition of oral leukoplakia adopted by the World Health Organization is "white plaques of questionable risk having excluded (other) known diseases or disorders that carry no increased risk for cancer". However, this definition is inconsistently applied in the medical literature, and some refer to any oral white patch as "leukoplakia". The term has been incorrectly used for white patches of any cause (rather than specifically referring to idiopathic white patches) and also to refer only to white patches which have a risk of cancerous changes. It has been suggested that leukoplakia is an unhelpful term since there is so much inconsistency surrounding its use, and some clinicians now avoid using it at all. Biopsy Tissue biopsy is usually indicated to rule out other causes of white patches and also to enable a detailed histologic examination to grade the presence of any epithelial dysplasia. This is an indicator of malignant potential and usually determines the management and recall interval. The sites of a leukoplakia lesion that are preferentially biopsied are the areas that show induration (hardening) and erythroplasia (redness), and erosive or ulcerated areas. These areas are more likely to show any dysplasia than homogeneous white areas. Brush biopsy/exfoliative cytology is an alternative to incisional biopsy, where a stiff brush is scraped against the lining of the mouth to remove a sample of cells. This is then made into a smear which can be examined microscopically. Sometimes the biopsy site can be selected with adjunct methods which aim to highlight areas of dysplasia. Toluidine blue staining, where the dye is preferentially retained by dysplastic tissue, is sometimes used, but there is high false positive rate. Other methods involve the use of luminescence, relying on either the property of normal autoflorescent molecules in mucosa such as collagen and keratin which is lost from areas of dysplasia or carcinoma under blue light or by initially staining of the mucosa with toluidine blue or dilute acetic acid and examination under white light. Histologic appearance Leukoplakia has a wide range of possible histologic appearances. The degree of hyperkeratosis, epithelial thickness (acanthosis/atrophy), dysplasia and inflammatory cell infiltration in the underlying lamina propria are