Anal cancer

Also known as: Cancer - anus, Squamous cell carcinoma - anal or HPV - anal cancer


Anal cancer is cancer that starts in the anus. The anus is the opening at the end of your rectum. The rectum is the last part of your large intestine where solid waste from food (stool) is stored. Stool leaves your body through the anus when you have a bowel movement.

Anal cancer is fairly rare. It spreads slowly and is relatively easy to treat before it spreads.


Anal cancer can start anywhere in the anus. Where it starts determines the kind of cancer it is.

  • Squamous cell carcinoma. This is the most common type of anal cancer. It starts in cells that line the anal canal and grow into the deeper tissue.
  • Cloacogenic carcinoma. Almost all the rest of anal cancers are tumors that start in cells lining the area between the anus and rectum. Cloacogenic carcinoma looks different than squamous cell cancers, but behaves similarly and is treated the same.
  • Adenocarcinoma. This type of anal cancer is rare in the United States. It starts in the anal glands below the anal surface and is often more advanced when it is found.
  • Skin cancer. Some cancers form outside the anus in the perianal area. This area is mainly skin. The tumors here are skin cancers and are treated as skin cancer.

The cause of anal cancer is unclear. However, there is a link between anal cancer and the human papillomavirus or HPV infection. HPV is a sexually transmitted virus that has been linked to other cancers as well.

Other major risk factors include:

  • HIV infection. Anal cancer is more common among HIV-positive men who have sex with other men.
  • Sexual activity. Having many sexual partners and having anal sex are both major risks. This may be due to the increased risk of HPV and HIV infection.
  • Smoking. Quitting will reduce your risk of anal cancer.
  • Weakened immune system. AIDs, organ transplants, certain medicines, and other conditions that weaken the immune system increase your risk.
  • Age. Most people who have anal cancer are age 50 or older. It is rare in someone younger than age 35.
  • Gender and race. Anal cancer is more common among women than men in most groups. More African American males get anal cancer than females.


Rectal bleeding, often minor, is one of the first signs of anal cancer. Often, a person mistakenly thinks the bleeding is caused by hemorrhoids.

Other early signs and symptoms include:

  • A lump in or near the anus
  • Anal pain
  • Itching
  • Discharge from the anus
  • Change in bowel habits
  • Swollen lymph nodes in the groin or anal region

Exams and Tests

Anal cancer is often found by a digital rectal exam (DRE) during a routine physical exam.

Your health care provider will ask about your health history, including sexual history, past illnesses, and your health habits. Your answers can help your provider understand your risk factors for anal cancer.

Your provider may ask for other tests. They might include:

If any tests show you have cancer, your provider will likely do more testing to "stage" the cancer. Staging helps show how much cancer is in your body and whether it has spread.

How the cancer is staged will determine how it is treated.


Treatment for anal cancer is based on:

  • The stage of the cancer
  • Where the tumor is located
  • Whether you have HIV or other conditions that weaken the immune system
  • Whether the cancer has resisted initial treatment or has come back

In most cases, anal cancer that hasn't spread can be treated with radiation therapy and chemotherapy together. Radiation alone can treat the cancer. But the high dosage that's needed can cause tissue death and scar tissue. Using chemotherapy with radiation lowers the dose of radiation that's needed. This works just as well to treat the cancer with fewer side effects.

Surgery is another option for earlier stages.

For stage 0 to stage II cancer, surgery to remove the tumor or abnormal cells is all that is needed. Your provider will work to preserve the anal sphincter. This is the muscle that opens and closes the anus.

For more advanced cancer, surgery will remove tissue in several areas where the cancer has spread. This may involve removing the anus, the rectum, and part of the colon. The new end of the large intestine will then be attached to an opening (stoma) in the abdomen. The procedure is called a colostomy. Stools moving through the intestine drain through the stoma into a bag attached to the abdomen.

Support Groups

Cancer affects more than your body. It affects how you feel about yourself and your life. You can ease the stress of illness by joining a cancer support group. Sharing with others who have common experiences and problems can help you feel less alone.

You can ask your provider or the staff at the cancer treatment center to refer you to an anal cancer support group.

Outlook (Prognosis)

Anal cancer spreads slowly. With early treatment, about 70% of people with anal cancer are cancer-free after 5 years.

Possible Complications

You may have side effects from surgery, chemotherapy, or radiation therapy.

When to Contact a Medical Professional

See your provider if you notice any of the possible symptoms of anal cancer, especially if you have any of the risk factors for it.


Since the cause of anal cancer is unknown, it's not possible to completely prevent it. But you can take steps to lower your risk.

  • Avoid HPV and HIV infections. People who have sex with many partners or have unprotected anal sex are at high risk of these infections. Using condoms can offer some protection, but not total protection. Talk with your provider about your options.
  • Ask your provider about the HPV vaccine and if you should get it.
  • DO NOT smoke. If you do smoke, quitting can lower your risk of anal cancer as well as other diseases.


Anal Cancer Treatment (PDQ). National Cancer Institute. Updated: 5/12/15. Available at: Available at: Accessed: 7/7/2015.

Belkacémi Y, Berger C, Poortmans P, Piel G, Zouhair A, et al. Management of primary anal canal adenocarcinoma: a large retrospective study from the Rare Cancer Network. Int J Radiat Oncol Biol Phys. 2003 Aug 1;56(5):1274-83. PMID: 12873671

Darragh TM, Berry JM, Jay N, Anal disease. In: Apgar BS, Brotzman GL, Spitzer S, eds. Colposcopy: Principles and Practice. 2nd ed. Philadelphia, PA: Elsevier Saunders; 2008:chap 23.

Glynne-Jones R, Renehan, A. Current treatment of anal squamous cell carcinoma. Hematol Oncol Clin N Am. 2012 Dec;26(6):1315-50. PMID: 23116582

Review date:
July 10, 2014
Reviewed by:
Christine Zhang, MD, Medical Oncologist, Fresno, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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