Frequently Asked Questions

Don’t see your question? Ask us!

What is the anus? What is anal cancer?

The anus is the very end of the digestive system, just below the colon and the rectum. Anal cancer is cancer of the skin lining the anus. It is different from colorectal cancer, and sometimes missed during routine colonoscopies (exams to look for colorectal cancer).

What causes anal cancer?

About 90% of anal cancers are caused by the Human Papillomavirus or HPV. There are many strains or types of HPV and not all of them cause cancer. Most cancers of the cervix and anus are caused by HPV strains 16 and 18. Other HPV strains cause genital warts. HPV is the most common sexually transmitted disease and most people are exposed to HPV over their lifetime. HPV infection usually goes away on its own. However, when the immune system is damaged by HIV, HPV infection can last longer and cause changes to the skin inside the anus called “dysplasia.” Over time, some of these HPV-damaged cells (which are called “High-Grade Squamous Intraepithelial Lesions” or HSIL) can develop into cancer. HSIL is not the same as cancer, but it is a warning sign that cancer may one day develop in that spot. We don’t know why some HSIL go away on their own while others get worse and develop into cancer.

Who can get anal cancer?

Anyone can get anal cancer, but it is much more common for people who are HIV-positive than HIV-negative. For perspective, in HIV-negative people the chance of developing anal cancer is 1-2 people per 100,000. In HIV-positive people it is between 30-131 per 100,000. (The rate in HIV positive women is lower than in men.) Even those on successful antiretroviral therapy have a higher risk of anal cancer than HIV-negative people. People who have never had anal sex can still get anal cancer.

How often do people with HIV get anal cancer?

People living with HIV (PWHIV) have the highest risk of anal cancer. The lifetime risk of anal cancer can be as high as 10% of people with anal high grade squamous intraepithelial lesions, or HSIL. In the general population, anal cancer occurs most often in women.

What is anal pre-cancer (anal HSIL)?

Anal pre-cancer is called HSIL. Anal HSIL is an area of abnormal skin growth of the anus. Anal HSIL and anal cancer is caused by the human papillomavirus (HPV). Some types of this virus cause warts and some types cause pre-cancer and cancer. Most of the time, anal HSIL does not progress to anal cancer. However, it can become anal cancer in about 10% of PWHIV with HSIL.

What are the signs of anal cancer?

The early stages of anal cancer usually have no symptoms which means most people are unaware when they begin to develop cancer. In later stages the most common symptom reported is pain, which can be felt constantly or felt only when using your anus to go to the bathroom or have sex. A lump or bleeding from the anus can also be symptoms of anal cancer. Anal cancer is often misdiagnosed as a hemorrhoid. If you are having any of these symptoms it’s important to tell your doctor.

How do doctors normally screen for and diagnose anal HSIL and cancer?

Doctors may do an anal pap smear (a swab rubbed against the skin inside the anus) to find abnormal cells. High resolution anoscopy, or HRA, is an anal exam with a special microscope to find pre-cancer and cancer. During HRA, the health care provider takes a biopsy (cuts off a small piece of skin) if any areas look abnormal. Another doctor looks at the tissue under a microscope to decide if the biopsy is HSIL or cancer.

How is anal cancer treated?

When caught early, anal cancer usually responds well to treatment. Some small cancers can be removed surgically. However, once the cancer spreads treatment may require a combination of drugs (chemotherapy), radiation, and surgery. The earlier anal cancer is found and treated, the fewer side effects from treatment. 

Is there a cure for anal cancer?

Removing the affected areas can “cure” anal cancer but there are often long term side effects from the surgery, radiation, and chemotherapy. People with a history of anal cancer need to be checked regularly to make sure the cancer doesn’t grow back.

What are the risk factors for anal cancer?

  • Infection with certain strains of Human Papillomavirus (HPV)
  • Age - risk goes up as you get older
  • Having a low CD4 count in the past
  • Smoking
  • For women: A history of HPV related cervical and vulvar dysplasia and/or cancers
  • History of genital warts


What's a good website with more anal cancer info?

What's it like to have anal cancer?

Follow the links below to hear from men and women who have had anal cancer:

  • Thriver Stories. These are the stories of anal cancer thrivers. We prefer to use the word thriver because surviving isn’t enough — we believe that every person with cancer should be empowered with the resources to thrive. We welcome you to read the experiences of others who have had anal cancer and encourage you to send your own stories to info [at] Please note that these individuals speak about their treatment plans. Speak to your doctor about what is right for you.
  • Anal cancer Survivor - David's Story. David shares his personal experience with anal cancer: his initial reaction to the diagnosis; the battle coming to terms with it; facing the treatment options and finally overcoming the cancer.
  • Anal Cancer: Living Life Four Months At A Time. Nearly two years ago, Michele Longabaugh was told she had anal cancer. Yet, she says, she had none of the risk factors. This is part one of a two-part series focusing on anal cancer and how one woman lives life four months at a time and copes with the stigma that comes with it. The four months is the length between her CT scans that will tell her if her cancer has returned. Michele agreed to do the story and has created an incredible and intimate blog that details her struggle with anal cancer. When you access it, go to the archives and start at the beginning. It was and is Michele's way of coping with a disease that no one wants to talk about.
  • Living and Thriving After Treatment for Anal Cancer: Addressing Long-Term Treatment Side Effects. At an educational forum for anal cancer survivors, a panel of experts discussed side effects often experienced by individuals treated for anal cancer. Panelists addressed the short and long-term quality of life effects after chemotherapy and radiation and management of these side effects. This event was sponsored by The HPV and Anal Cancer Foundation, the UCSF Helen Diller Family Comprehensive Cancer Center, and the Farrah Fawcett Foundation. Co-sponsors include the UCSF Alliance Health Project, Project Inform, the Shanti Project, and the International Anal Neoplasia Society.