Anal cancer is an uncommon cancer occurring in the tissues that make up the opening through which stool passes out of the body.
The anus is the opening at the end of the large intestine (rectum) through which solid waste passes out of the body. The anus is a junction between two types of tissues: mucosa, which lines the intestines, and skin. Cancer located at the junction between the rectum and anus is called "anal canal cancer" (also known as transitional-cell, squamous, epidermoid, or basal cell cancer). Cancer located near the external skin is called "anal margin cancer." Anal canal cancer is more common in women, and anal margin cancer is more common in men.
Approximately 3, 400 cases of anal cancer were diagnosed in the United States in 2000. Anal cancer accounts for 1.5% of the cancers of the digestive system. The average age at diagnosis is 62 years. Most anal cancers are squamous cell carcinomas.
Women are much more likely than men to develop anal cancer. Anal cancer is more prevalent in Caucasians than other races.
Causes and symptoms
The previously-held belief that anal cancer is caused by the chronic irritation associated with cracks (fissures), hemorrhoids, and abnormal passageways (fistulae), is falling out of favor. It is now believed that most cases of anal cancer are caused by human papilloma virus (HPV), a sexually-transmitted virus that can cause genital warts. Cancer is caused when the normal mechanisms that control cell growth become disturbed, causing the cells to grow continually without stopping. This may be the result of damage to the DNA in the cell or viral infection.
Symptoms of anal cancer may include:
bleeding from the anus
pain around the anus
the sensation of anal pressure or a mass
straining to pass stool (rectal tenesmus)
Belinda Rowland Ph.D., The Gale Group Inc., Gale, Detroit,