Overview

of Anal Cancer

Anal cancer is relatively uncommon. The American Cancer Society estimates about 8,200 individuals will be diagnosed in 2017.  The number of individuals developing anal cancer has been rising for many years and the risk of being diagnosed with anal cancer during one’s lifetime is about 1 in 500. Current treatment for anal cancer can be very effective especially when then cancer is detected early.1

Anal cancer starts in the anus, which is the opening at the lower end of the intestines.  This opening is connected to the rectum by the anal canal. The anal canal is about an inch and a half long. It goes from the rectum to the anal verge where the canal meets the outside skin at the anus.  Most anal cancers start in the squamous cells in the inner lining of the anal canal called the mucosa.

The anal canal is surrounded by a sphincter which is a circular muscle that keeps feces from coming out until it relaxes during a bowel movement.  Anal cancers are often divided into two groups, which are sometimes treated differently:

  • Cancers of the anal canal (above the anal verge)
  • Cancers of the anal margin (below the anal verge)

Anal cancers can also begin in glands that make mucus, which acts as a lubricating fluid. These are called adenocarcinomas and a treated like colo-rectal cancer.   This content focuses on invasive anal squamous cell carcinomas, which account for the vast majority of anal cancers.1,2,3

Next: Symptoms & Signs

References


1 American Cancer Society. Cancer Facts & Figures 2016.

2 National Cancer Institute Fact Sheet. Human Papillomaviruses and Cancer: Questions and Answers.

3 https://www.cancer.net/cancer-types/anal-cancer/symptoms-and-signs