The anal canal is a short tube surrounded by muscle at the end of your rectum. The rectum is the bottom section of your colon large intestine. When you have a bowel movement, stool leaves your body from the rectum through the anal canal. As the cancer grows, it may stay in nearby tissues or spread to other parts of the body, a process called metastasis. Anal cancer starts in the cells around or just inside the anal opening.
Most anal cancers seem to be linked to infection with the human papillomavirus HPV. While HPV infection seems to be important in the development of anal cancer, the vast majority of people with HPV infections do not get anal cancer. A great deal of research is now being done to learn how HPV might cause anal cancer. There is good evidence that HPV causes many anal squamous cell carcinomas.
Anal cancer is a type of cancer that forms in tissues of the anus. The anus is the opening of the rectum to the outside of the body and at the end of the GI tract. Sometimes anal cancer causes no symptoms at all. But bleeding is often the first sign of the disease. The bleeding is usually minor.
Researchers continue to investigate the causes of anal cancer. Known risk factors that have been identified include chronic infection with high-risk types of human papillomavirus HPV , gender and age. HPV, a collection of more than viruses spread primarily by contact during vaginal, oral or anal sexual activity, is responsible for the majority of anal cancers. HPV may be asymptomatic for years, and persistent HPV infections may cause cell changes that, left untreated, may become cancer.