The anal canal runs from the end of the rectum to the external orifice of the anus that gives rise to an unusual cancer, suspected to be caused by the human papilloma virus. It mostly occurs in those who practice anal sexual intercourse but can also occur in those on immuno-suppressing therapy. It occurs in both men and women. There is frequently a history of multiple sexual partners, a history of anal warts and sexually transmitted diseases like hepatitis, AIDS, and gonorrhea.
Smoking also appears to be a predisposing factor.
About 3400 cases occur each year. It is not predisposed by hemorrhoids. The cancer is a squamous cell type and usually presents with rectal itching and bleeding. When the anus is examined, warts and erosions from anal sexual intercourse may be present around or near the cancer. The best treatments are a combination of radiation therapy and chemotherapy.