Neoplasms of the anus.

Anal cancers can be grouped into three major categories. First, anal margin lesions are usually well-differentiated, keratinized squamous cell carcinomas that are amenable to local treatment measures. Second, anal canal cancers distal to the dentate line are mostly epidermoid, nonkeratinizing, moderately differentiated tumors. They are usually best treated with a multimodality approach using chemoradiotherapy and reserving surgery for clinical failures. Third, cancers arising in the ATZ are usually adenocarcinomas, and their treatment depends upon local factors. APR is in order for locally aggressive lesions, but newer protocols are studying multimodality therapy for this entity as well. Other, less common cancers of this region should be evaluated based upon their biologic potential and local involvement, with treatments selected accordingly.