What is anal cancer?
Anal cancer is a rare form of cancer that develops in the tissues of the anus, which is the opening at the end of the rectum through which stool passes. The anus consists of the outer layers of skin and the large intestine. The anal canal is shaped like a tube and is controlled by muscles that open and close.
Anal cancer incidence
About one in 500 men and women will develop anal cancer during their lifetime, according to the American Cancer Society.
An estimated 7,270 new cases of anal cancer were diagnosed in 2014. Of those cases, approximately 4,630 were in women and 2,640 were in men. While anal cancer is far less common than colorectal cancer, the number of cases has been growing due to human papillomavirus (HPV) infections. HPV is the most common sexually transmitted infection and is responsible for 95 percent of anal cancer cases, according to the National Cancer Institute.