Anal cancers are those that arise in the anatomic area extending from the anorectal ring to a zone about halfway between the dentate line and the anal verge, accounting for 1%-2% of malignant tumors of the large bowel.

Risk factors for development of anal cancer include infection by the human papillomavirus (HPV) leading to condyloma acuminata, which may progress to anal intraepithelial neoplasia and then squamous cell carcinoma. Also at higher risk are men who have anal intercourse with men and patients with AIDS due to their immunosuppressed status. Anal cancer is most common in middle-aged individuals, and women are more frequently affected than men.

Presenting symptoms include bleeding, pain, sensation of a perianal mass, or anal pruritus. Pathology depends on location: carcinomas arising proximal to the pectinate line are known as basaloid, cuboidal, or cloacogenic tumors; tumors arising distal to the pectinate line have a squamous cell histology.