Premalignant lesions of the upper aerodigestive tract: pathologic classification.

Intraepithelial neoplasia of the upper aerodigestive tract (UADT), including both histologically defined dysplasia and carcinoma in situ (CIS), appears to fall into two broad groups similar to intraepithelial neoplasia of other squamous mucosae, keratinizing and non-keratinizing. Keratinizing dysplasia/CIS is common in the UADT and uncommon in other sites such as the cervix. In general, keratinizing epithelial proliferation results in thick epithelium, usually with prominent superficial keratin expression with a whitish or "leukoplakic" clinical appearance. Although most clinical leukoplakic changes in the UADT mucosa do not represent neoplastic transformation and do not progress to invasive carcinoma, keratinizing dysplasia, defined by nuclear atypism and maturation alterations, has an appreciable progression to invasive carcinoma. Non-keratinizing dysplasia/CIS, common in the cervix, is less common in the UADT mucosa. In general, non-keratinizing epithelial alterations consist of a proliferation of incompletely differentiated cells as measured by a spectrum of maturation markers. These changes result in a thin epithelium which commonly has a red, or clinically "erythroplakic," appearance. Non-keratinizing dysplasias are less common, but are more likely to harbor high grade dysplasia or early invasive carcinoma.