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Anal Cancer: Introduction

The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer, skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening to let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1½ inches long.

Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus. The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

Risk factors include the following:

  • Being over 50 years old.
  • Being infected with human papillomavirus (HPV).
  • Having many sexual partners.
  • Having receptive anal intercourse (anal sex).
  • Frequent anal redness, swelling, and soreness.
  • Having anal fistulas (abnormal openings).
  • Smoking cigarettes.

Treatment options depend on the following:

  • The stage of the cancer.
  • Where the tumor is in the anus.
  • Whether the patient has human immunodeficiency virus (HIV).
  • Whether cancer remains after initial treatment or has recurred.