Squamous cell carcinoma of the upper aerodigestive tract: dysplasia and select variants.

Upper aerodigestive tract (UADT) mucosal premalignant lesions include non-keratinizing and keratinizing intraepithelial dysplasia. The keratinizing type of intraepithelial dysplasia represents the majority of UADT dysplasias. Historically, grading of UADT dysplasias has followed a three tier system to include mild, moderate and severe dysplasia. Recent recommendations have introduced a two tier grading scheme to including low-grade (ie, mild dysplasia) and high-grade (moderate and severe dysplasia/carcinoma in situ) providing for better consensus among pathologists in the interpretation of such dysplastic lesions. Squamous cell carcinoma is the most common malignant neoplasm of the UADT. Several variants of squamous cell carcinoma are recognized among which the more common types include papillary squamous cell carcinoma, verrucous carcinoma, spindle cell squamous cell carcinoma (sarcomatoid carcinoma) and basaloid squamous cell carcinoma. Each of these variants of squamous cell carcinoma poses diagnostic challenges and each correlates to specific therapy and prognosis. This review details the proposed update in the grading of UADT dysplasia to a two-tiered system as well as providing the key diagnostic features for select variants of squamous cell carcinoma.