What is anal cancer?

Cancer describes a set of diseases in which normal cells in the body, through a series of genetic changes, lose the ability to control their growth. As cancers grow, they invade the tissues around them (local invasion). They may also spread to other locations in the body via the blood vessels or lymphatic channels where they may implant and grow (metastases)

The anal canal is a passage that connects the rectum to the outside of the body. The anal canal is surrounded by muscles that keep the anal canal closed except for when the muscles are relaxed during a bowel movement. Anal cancer arises from the cells around the anal opening or in the anal canal just inside the anal opening. Anal cancers arise from skin cells and are called squamous cell carcinomas. Cells that are becoming malignant but have not invaded deep to the skin are referred to as “high grade dysplasia”, “carcinoma-in-situ” or “Bowen’s disease”.

How common is anal cancer?

Anal cancer is fairly uncommon. It accounts for about 1-2% of gastrointestinal cancers. About 4,000 new cases of anal cancer are diagnosed each year in the U.S.A., about half in women. Approximately 600 people will die of the disease each year. This may be compared to 140,000 new cases of colorectal cancer with 50,000 deaths per year.

Who is at risk?

Anal cancer is commonly associated with the human papilloma virus (HPV). This virus causes warts in and around the anus and on the cervix in women. It is associated with an increased risk of cervical cancer in women.