Anal cancer is a rare form of cancer in which malignant cells are found in the outer part of the anus or in the anal canal. The anus is the opening at the end of the rectum through which waste is eliminated. Cancer in the outer part of the anus is more likely to occur in men while women are more often afflicted by cancer of the anal canal. Each year about 3,400 new cases of anal cancer are diagnosed in the United States. An estimated 410 people will die of anal cancer this year. Although rare, anal cancer appears to be on the rise.
Cancerous anal tumors include squamous cell carcinomas, adenocarcinomas, basal cell carcinomas and malignant melanomas. Squamous cell carcinomas, which account for about half of all anal cancers diagnosed, usually begin in the surface cells that line the anus and most of the anal canal. Adenocarcinomas begin in the glands in the anal area and account for about 15 percent of anal cancers. A small percentage of anal cancers are basal cell carcinomas. Melanomas are extremely rare (about 1 to 2 percent of anal cancers) because they tend to occur on parts of the body that are exposed to sunlight. Most anal melanomas are found at a late stage because they cannot easily be seen.
