Anal cancer is cancer of the anus. This is the canal at the end of the large intestine, below the rectum. The anal sphincter is a muscular ring that controls and allows for bowel movements.

The Anus
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Cancer occurs when cells in the body divide without control or order. Eventually, these uncontrolled cells form a growth or tumor. The term cancer refers to malignant growths. These growths can invade nearby tissues and spread to other parts of the body.

There is evidence that human papillomavirus (HPV) infection is linked to many anal cancers. However, most people who have been infected with HPV do not get anal cancer.