Update on Oral Epithelial Dysplasia and Progression to Cancer

Precursor lesions of the upper aerodigestive tract are similar regardless of site and can be defined as altered epithelial lesions, which have an increased likelihood of progressing to squamous cell carcinoma. In the oral cavity the most common lesions recognised as potentially malignant are leukoplakia and erythroplakia, but it is also apparent that as many as 50% of oral squamous cell carcinomas arise from apparently clinically normal mucosa. The prognostic significance of an individual lesion is difficult to determine, and none of the currently available molecular markers have proved to be prognostically significant and none have yet been evaluated in large prospective studies. At present therefore, the gold standard for the assessment of oral potentially malignant lesions is microscopic evaluation of haematoxylin and eosin stained sections for the presence of architectural and cytological changes, which are generally referred to as epithelial dysplasia. Some texts use the terms squamous intraepithelial neoplasia (SIN) or squamous intraepithelial lesions (SIL; Table 1) [1]. The categories under each scheme are similar, but the terminology is not exactly synonymous. In the oral cavity, use of the SIL terminology of ‘atypical hyperplasia’ may lead to confusion because of the large number of common benign hyperplastic lesions, which may be encountered. In oral and maxillofacial pathology therefore, oral epithelial dysplasia is regarded as the standard terminology [2, 3]. Criteria for the Diagnosis of Oral Epithelial Dysplasia