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Oral leukoplakia (OL) is the most common potentially malignant disorder of the oral mucosa (Neville and Day, 2002; Haya-Fernández et al., 2004; WHO, 2005). Besides oral leukoplakia, actinic cheilitis, lichen planus, and erythroplakia are also considered potentially malignant conditions affecting the oral cavity. These lesions can precede oral squamous cell carcinoma, which is the most common malignancy of the oral cavity (Neville and Day, 2002; Haya-Fernández et al., 2004). It is believed that those conditions are reasonably classified as "potentially malignant " as it has been observed that some lesions evolved to malignant ones during follow-up. In addition, typical alterations of potentially malignan