Squamous Dysplasia: Pathogenesis and Histological Grading

In the upper aerodigestive tract (UADT), the most common lesions encountered by the otolaryngologist and the pathologist relate to alterations of the surface squamous epitheLium. A common histological alteration confronted by pathologists is intraepitheLial squamous dysplasia. IntraepitheLial squamous dysplastic changes represent a spectrum of abnormal epitheLial maturation and cellular aberrations that may or may not precede an invasive carcinoma. The grading of UADT intraepitheLial squamous dysplasia includes mild, moderate, and severe depending on the extent of involvement of the surface epitheLium. While conceptually simple, the appLication of this grading system is fraught with subjectivity and lack of reproducibiLity among pathologists. This is primarily due to the fact that the majority of squamous dysplasias of the UADT occur in the setting of surface keratinization (the so-called keratinizing dysplasias) in which invasive carcinoma can develop in the setting of dysplastic changes Limited to the lower zone epitheLium without full-thickness intraepitheLial dysplasia (i.e., carcinoma in situ). In this article, we discuss the pathogenesis and histopathologic spectrum UADT squamous dysplasia.