Anal adenocarcinoma: a comprehensive review.

Adenocarcinoma of the anal canal is a rare form of a rare tumor. It remains less prevalent than both basaloid and keratinizing tumors of the anal canal. Within the category of anal adenocarcinomas, uniformity in histology, biology, or etiology is lacking. This makes subdivision of this rare entity by various parameters necessary. Several etiologic associations have been described, such as chronic fistula-in-ano, anal Crohn's disease, and anal sexual intercourse, raising the issue of cancer prevention and early detection. Various available therapeutic options are also discussed with emphasis on the seemingly promising results of preoperative chemo- and radiation therapy. Because of the rarity and apparent heterogeneity of this tumor, no comparative or analytic epidemiologic studies have been conducted that might resolve these issues. Whether histology differentiates anal adenocarcinoma from anal squamous or cloacogenic tumors in the determination of natural history and allocation to optimal therapy remains unclear. It may be that the gross anatomic location of the tumor alone determines the above and histology is superfluous.