The etiology and epidemiology of anal cancer.

The anatomic definitions for anal cancer (canal versus margin) are made based on the relationship of the tumor to the anal verge. This method had led to confusion for some providers. A modification in the terminology is proposed that includes intra-anal, perianal, and skin as categories. The cause of anal carcinoma remains to be fully elucidated, and HPV seems to play a central role in this process. The incidence of anal cancers has increased, which is related to the evolution of HIV and AIDS, and their treatment. The accurate pathologic analysis of anal tumors is complex and is significantly aided by close communication between clinician and pathologist.