Anal cancer

Facts

Most people with anal cancer are cured, especially if their cancer is diagnosed early. No matter what type or stage of anal cancer you have, treatments are available. 

Seattle Cancer Care Alliance (SCCA) offers comprehensive anal cancer treatment from a team of experts who specialize in gastrointestinal cancers.

What is anal cancer?

Anal cancer occurs when cells begin to grow abnormally in:

  • The anus — the opening to the outside of the body at the end of the large intestine, below the rectum
  • The anal canal — the inch-and-a-half of tube inside the body that connects the rectum to the anus

Several layers and types of cells make up the tissues in this area. So different types of cancer can develop here, depending on which layer of cells is affected.

Whatever the type, anal cancer cells do not respond to regular cell growth, division and death signals like they are supposed to. They also don’t organize normally. Instead they grow into a tumor, which may break through surrounding layers of cells.

Types

Most anal cancers are one of these two types.

Starts in thin, flat cells (squamous cells) in the skin and linings of the body. It can start in the skin around the anus (perianal skin) and in the outer lining of the anal canal. This is the most common type of anal cancer.

Starts in glands. Anal adenocarcinoma can start in cells that line the upper anal canal and in glands under the anal lining that make mucus.

Symptoms

Anal cancer may not cause any symptoms, or it may not cause symptoms until it’s advanced. Symptoms may include:

  • Bleeding, pain or pressure in your anal area
  • Itching, swelling or a lump near your anus
  • A change in bowel habits or diameter of your stool
  • Discharge from your anus that’s not normal
  • Swollen lymph nodes in your groin

These symptoms may be caused by conditions other than cancer. If you have any of the symptoms above, or other symptoms that concern you, see your doctor to find out the reason. 

If you do have anal cancer, doctors are more likely to find it early — when it’s easier to treat — if you’re evaluated sooner rather than later.

Diagnosing

If you have signs or symptoms that could be from anal cancer, your doctor will start by asking about your medical history and family history and doing a physical exam. You may also need one or more of these procedures:

  • Digital rectal exam — Your doctor inserts a lubricated, gloved finger into your anus to feel for abnormal areas or masses. 

  • Anoscopy — Your doctor inserts a thin, short, lighted tube called an anoscope through your anus into the lower part of your rectum to look for any abnormalities.

  • Flexible sigmoidoscopy — Your doctor looks at your anus and rectum using a thin, lighted tube called a sigmoidoscope.

  • Biopsy — During anoscopy, your doctor may remove small samples of tissue (or an entire tumor, if it’s small). A pathologist examines the cells under a microscope. This is the only way to tell whether you have anal cancer.

  • Imaging studies — If cancer is found, your doctor may also want you to have imaging studies, such as an X-ray, ultrasound, computed tomography (CT) scan, magnetic resonance imaging (MRI) scan or positron-emission tomography (PET) scan, to learn more about whether your cancer has spread.

Stages

The treatment that your doctors recommend for anal cancer will be based in part on the stage of your cancer. The stage depends on:

  • How large your cancer is

  • Whether the cancer has invaded nearby organs

  • Whether the cancer has spread to lymph nodes

  • Whether the cancer has spread to distant parts of your body

Anal cancers are grouped into stages I through IV, with stage I being the least advanced and stage IV being the most advanced.

What causes anal cancer?

There isn't any known cause for anal cancer, but several factors may contribute to its development.

Risk factors

These factors may affect your risk for anal cancer:

  • Age — Most people who develop anal cancer are over age 50.

  • Human papillomavirus (HPV) — HPV can cause genital and anal warts (though most people with HPV don’t have warts), and some strains of the virus can cause cancer of the anus, cervix, vagina, vulva or penis. HPV is spread by skin-to-skin contact. Women who have had cervical, vaginal or vulvar cancer are more likely to get anal cancer, possibly because all these cancers can be caused by HPV. (Most people with HPV do not get cancer.)

  • Anal irritation — You may be at greater risk if you often have redness, swelling or soreness around your anus.

  • Anal fistula — A fistula is an abnormal tunnel that forms in the body. An anal fistula connects your anus to the outside of your body. Pus or liquid may drain from this tunnel. 

  • Smoking — Smoking is linked to several types of cancer, not just lung cancer. Smokers are about eight times more likely to get anal cancer than nonsmokers.

  • Lowered immunity — Any condition that lowers your immune function makes it more difficult for your body to fight disease and more likely that you will develop cancer. 

  • Human immunodeficiency virus (HIV) — Being infected with HIV, the virus that causes acquired immune deficiency syndrome (AIDS), may raise the risk for anal cancer. 

  • Sexual activity — Having many sexual partners increases the risk for HPV, HIV and anal cancer. Also, both men and women who receive anal sex are at increased risk for anal cancer.

How common is anal cancer?

About 8,600 people are diagnosed with anal cancer in the United States each year. 

Overall, women are more likely to get anal cancer than men are. African-Americans are more likely than European Americans to develop the disease. Among African-Americans, men are more likely to get this type of cancer than women are.