The anus is where stool leaves your body when you go to the bathroom. It is made up of your outer layers of skin and the end of your large intestine. Anal cancer is a disease in which cancer cells form in the tissues of the anus.

Anal cancer is rare. It is more common in smokers and people over 50. You are also at higher risk if you have HPV, have anal sex, or have many sexual partners.

Symptoms include bleeding, pain, or lumps in the anal area. Anal itching and discharge can also be signs of anal cancer.

Doctors use tests that examine the anus to diagnose anal cancer. They include a physical exam, endoscopy, ultrasound, and biopsy.

Treatments include radiation therapy, chemotherapy, and surgery.

KEY POINTS

• Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.
• Being infected with the human papillomavirus (HPV) increases the risk of developing anal cancer.
• Signs of anal cancer include bleeding from the anus or rectum or a lump near the anus.
• Tests that examine the rectum and anus are used to detect (find) and diagnose anal cancer.
• Certain factors affect the prognosis (chance of recovery) and treatment options.

Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.

The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening and let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1-1½ inches long.

The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

Risk factors for anal cancer include the following:

• Being infected with human papillomavirus (HPV).
• Having a condition or disease that causes a weakened immune system, such as human immunodeficiency virus (HIV) or an organ transplant.
• Having a personal history of vulvar, vaginal, or cervical cancers.
• Having many sexual partners.
• Having receptive anal intercourse (anal sex).
• Smoking cigarettes.

These and other signs and symptoms may be caused by anal cancer or by other conditions. Check with your doctor if you have any of the following:

• Bleeding from the anus or rectum.
• A lump near the anus.
• Pain or pressure in the area around the anus.
• Itching or discharge from the anus.
• A change in bowel habits.

The following tests and procedures may be used:

• Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Digital rectal examination (DRE): An exam of the anus and rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual.

• Anoscopy: An exam of the anus and lower rectum using a short, lighted tube called an anoscope.
• Proctoscopy: A procedure to look inside the rectum and anus to check for abnormal areas, using a proctoscope. A proctoscope is a thin, tube-like instrument with a light and a lens for viewing the inside of the rectum and anus. It may also have a tool to remove tissue samples, which are checked under a microscope for signs of cancer.
• Endo-anal or endorectal ultrasound: A procedure in which an ultrasound transducer (probe) is inserted into the anus or rectum and used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
• Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. If an abnormal area is seen during the anoscopy, a biopsy may be done at that time.

Certain factors affect the prognosis (chance of recovery) and treatment options.

The prognosis depends on the following:

• The size of the tumor.
• Whether the cancer has spread to the lymph nodes.

The treatment options depend on the following:

• The stage of the cancer.
• Where the tumor is in the anus.
• Whether the patient has human immunodeficiency virus (HIV).
• Whether cancer remains after initial treatment or has recurred.

Endoscopic examination, therapy or surgery of the rectum.

After anal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the anus or to other parts of the body.

The process used to find out if cancer has spread within the anus or to other parts of the body is called staging. The information gathered from this staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests may be used in the staging process:

• • CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the abdomen, pelvis, or chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
  • Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
  • MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
  • PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
  • Pelvic exam: An exam of the vagina, cervix, uterus, fallopian tubes, ovaries, and rectum. A speculum is inserted into the vagina and the doctor or nurse looks at the vagina and cervix for signs of disease. A Pap test of the cervix is usually done. The doctor or nurse also inserts one or two lubricated, gloved fingers of one hand into the vagina and places the other hand over the lower abdomen to feel the size, shape, and position of the uterus and ovaries. The doctor or nurse also inserts a lubricated, gloved finger into the rectum to feel for lumps or abnormal areas.

  There are three ways that cancer spreads in the body.

  Cancer can spread through tissue, the lymph system, and the blood:

  • Tissue. The cancer spreads from where it began by growing into nearby areas.
  • Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
  • Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.

  Cancer may spread from where it began to other parts of the body.

  When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.

  • Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
  • Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.

  The metastatic tumor is the same type of cancer as the primary tumor. For example, if anal cancer spreads to the lung, the cancer cells in the lung are actually anal cancer cells. The disease is metastatic anal cancer, not lung cancer.

  The following stages are used for anal cancer:

  Stage 0

  In stage 0, abnormal cells are found in the mucosa (innermost layer) of the anus. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called high-grade squamous intraepithelial lesion (HSIL).

  Stage I

  In stage I, cancer has formed and the tumor is 2 centimeters or smaller.

  Stage II

  Stage II anal cancer is divided into stages IIA and IIB.

  • In stage IIA, the tumor is larger than 2 centimeters but not larger than 5 centimeters.
  • In stage IIB, the tumor is larger than 5 centimeters.

  Stage III

  Stage III anal cancer is divided into stages IIIA, IIIB, and IIIC.

  • In stage IIIA, the tumor is 5 centimeters or smaller and has spread to lymph nodes near the anus or groin.
  • In stage IIIB, the tumor is any size and has spread to nearby organs, such as the vagina, urethra, or bladder. Cancer has not spread to lymph nodes.
  • In stage IIIC, the tumor is any size and may have spread to nearby organs. Cancer has spread to lymph nodes near the anus or groin.

  Stage IV

  In stage IV, the tumor is any size. Cancer may have spread to lymph nodes or nearby organs and has spread to other parts of the body, such as the liver or lungs.

  Anal cancer can recur (come back) after it has been treated.

  The cancer may come back in the anus or other parts of the body, such as the liver or lungs.

What is prevention?

Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.

To prevent new cancers from starting, scientists look at risk factors and protective factors. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.

Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Regular exercise and a healthy diet may be protective factors for some types of cancer. Avoiding risk factors and increasing protective factors may lower your risk but it does not mean that you will not get cancer.

Different ways to prevent cancer are being studied, including:

• Changing lifestyle or eating habits.
• Avoiding things known to cause cancer.
• Taking medicines to treat a precancerous condition or to keep cancer from starting.

General Information About Anal Cancer

Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.

The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening and let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1-1½ inches long.

The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

Squamous cell carcinoma is the most common type of anal cancer.

In the United States, the most common type of anal cancer is squamous cell carcinoma. Studies show that human papillomavirus (HPV) infection is the main cause of this type of anal cancer.

Another type of anal cancer, called anal adenocarcinoma, is very rare and is not discussed in this summary.

In the United States, the number of new cases of anal cancer has increased in recent years.

From 2007 to 2016, new cases of anal cancer and deaths from anal cancer increased each year.

Anal Cancer Prevention

Avoiding risk factors and increasing protective factors may help prevent cancer.

Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.

The following are risk factors for anal cancer:

Anal HPV infection

Being infected with human papillomavirus (HPV) is the main risk factor for anal cancer. Being infected with HPV can lead to squamous cell carcinoma of the anus, the most common type of anal cancer. About nine out of every ten cases of anal cancer are found in patients with anal HPV infection.

Patients with healthy immune systems are usually able to fight HPV infections. Patients with weakened immune systems who are infected with HPV have a higher risk of anal cancer.

Certain medical conditions

History of cervical, vaginal, or vulvar cancer

Cervical cancer, vaginal cancer, and vulvar cancer are related to HPV infection. Women who have had cervical, vaginal, or vulvar cancer have a higher risk of anal cancer.

HIV infection/AIDS

Being infected with human immunodeficiency virus (HIV) is a strong risk factor for anal cancer. HIV is the cause of acquired immunodeficiency syndrome (AIDS). HIV weakens the body's immune system and its ability to fight infection. HPV infection of the anus is common among patients who are HIV-positive.

The risk of anal cancer is higher in men who are HIV-positive and have sex with men compared with men who are HIV-negative and have sex with men. Women who are HIV-positive also have an increased risk of anal cancer compared with women who are HIV-negative.

Studies show that intravenous drug use or cigarette smoking may further increase the risk of anal cancer in patients who are HIV-positive.

Immunosuppression

Immunosuppression is a condition that weakens the body's immune system and its ability to fight infections and other diseases. Chronic (long-term) immunosuppression may increase the risk of anal cancer because it lowers the body's ability to fight HPV infection.

Patients who have an organ transplant and receive immunosuppressive medicine to prevent organ rejection have an increased risk of anal cancer.

Having an autoimmune disorder such as Crohn disease or psoriasis may increase the risk of anal cancer. It is not clear if the increased risk is due to the autoimmune condition, the treatment for the condition, or a combination of both.

Certain sexual practices

The following sexual practices increase the risk of anal cancer because they increase the chance of being infected with HPV:

• Having receptive anal intercourse (anal sex).
• Having many sexual partners.
• Sex between men.

Men and women who have a history of anal warts or other sexually transmitted diseases also have an increased risk of anal cancer.

Cigarette smoking

Studies show that cigarette smoking increases the risk of anal cancer. Studies also show that current smokers have a higher risk of anal cancer than smokers who have quit or people who have never smoked.

The following protective factor decreases the risk of anal cancer:

HPV vaccine

The human papillomavirus (HPV) vaccine is used to prevent anal cancer, cervical cancer, vulvar cancer, and vaginal cancer caused by HPV. It is also used to prevent lesions caused by HPV that may become cancer in the future.

Studies show that being vaccinated against HPV lowers the risk of anal cancer. The vaccine may work best when it is given before a person is exposed to HPV.

It is not clear if the following protective factor decreases the risk of anal cancer:

Condom use

It is not known if the use of condoms protects against anal HPV infection. This is because not enough studies have been done to prove this.

Cancer prevention clinical trials are used to study ways to prevent cancer.

Cancer prevention clinical trials are used to study ways to lower the risk of developing certain types of cancer. Some cancer prevention trials are conducted with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are conducted with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.

The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include eating fruits and vegetables, exercising, quitting smoking, or taking certain medicines, vitamins, minerals, or food supplements.

KEY POINTS

• There are different types of treatment for patients with anal cancer.
• Three types of standard treatment are used:
  • Surgery
  • Radiation therapy
  • Chemotherapy
• New types of treatment are being tested in clinical trials.
  • Radiosensitizers
  • Immunotherapy
• Treatment for anal cancer may cause side effects.
• Patients may want to think about taking part in a clinical trial.
• Patients can enter clinical trials before, during, or after starting their cancer treatment.
• Follow-up tests may be needed.

There are different types of treatment for patients with anal cancer.

Different types of treatments are available for patients with anal cancer. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.

Three types of standard treatment are used:

Surgery

• Local resection: A surgical procedure in which the tumor is cut from the anus along with some of the healthy tissue around it. Local resection may be used if the cancer is small and has not spread. This procedure may save the sphincter muscles so the patient can still control bowel movements. Tumors that form in the lower part of the anus can often be removed with local resection.
• Abdominoperineal resection: A surgical procedure in which the anus, the rectum, and part of the sigmoid colon are removed through an incision made in the abdomen. The doctor sews the end of the intestine to an opening, called a stoma, made in the surface of the abdomen so body waste can be collected in a disposable bag outside of the body. This is called a colostomy. Lymph nodes that contain cancer may also be removed during this operation. This procedure is used only for cancer that remains or comes back after treatment with radiation therapy and chemotherapy.

Radiation therapy

Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:

• External radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer.
• Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer.

The way the radiation therapy is given depends on the type and stage of the cancer being treated. External and internal radiation therapy are used to treat anal cancer.

Chemotherapy

Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy).

New types of treatment are being tested in clinical trials.

This summary section describes treatments that are being studied in clinical trials. It may not mention every new treatment being studied. Information about clinical trials is available from the NCI website.

Radiosensitizers

Radiosensitizers are drugs that make tumor cells more sensitive to radiation therapy. Combining radiation therapy with radiosensitizers may kill more tumor cells.

Immunotherapy

Immunotherapy is a treatment that uses the patient's immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body's natural defenses against cancer. This cancer treatment is a type of biologic therapy.

Immune checkpoint inhibitor therapy is a type of immunotherapy.

• PD-1 and PD-L1 inhibitor therapy: PD-1 is a protein on the surface of T cells that helps keep the body’s immune responses in check. PD-L1 is a protein found on some types of cancer cells. When PD-1 attaches to PD-L1, it stops the T cell from killing the cancer cell. PD-1 and PD-L1 inhibitors keep PD-1 and PD-L1 proteins from attaching to each other. This allows the T cells to kill cancer cells. Pembrolizumab and nivolumab are types of PD-1 inhibitors.

Treatment for anal cancer may cause side effects.

For information about side effects caused by treatment for cancer, see our Side Effects page.

Patients may want to think about taking part in a clinical trial.

For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the standard treatment.

Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.

Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.

Patients can enter clinical trials before, during, or after starting their cancer treatment.

Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.

Clinical trials are taking place in many parts of the country. Information about clinical trials supported by NCI can be found on NCI’s clinical trials search webpage. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.

Follow-up tests may be needed.

Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated. Some tests will be repeated in order to see how well the treatment is working. Decisions about whether to continue, change, or stop treatment may be based on the results of these tests.

Some of the tests will continue to be done from time to time after treatment has ended. The results of these tests can show if your condition has changed or if the cancer has recurred (come back). These tests are sometimes called follow-up tests or check-ups.

Treatment of Stage 0 (Carcinoma in Situ)

Treatment of stage 0 is usually local resection.

Treatment of Stages I, II, and III Anal Cancer

Treatment of stage I, stage II, and stage III anal cancer may include the following:

• Local resection for tumors of the skin around the outside of the anus and tumors inside the anal opening that do not involve the anal sphincter.
• External-beam radiation therapy with chemotherapy.
• Radiation therapy alone.
• Abdominoperineal resection, if cancer remains or comes back after treatment with radiation therapy and chemotherapy. Other options may include treatment with additional chemoradiation therapy, chemotherapy alone, or immunotherapy.

Patients who have had treatment that saves the sphincter muscles may receive follow-up exams every 3 months for the first 2 years, including rectal exams with endoscopy and biopsy, as needed to check for recurrence.

Treatment of Stage IV Anal Cancer

Treatment of stage IV anal cancer may include the following:

• Palliative surgery to relieve symptoms and improve the quality of life.
• Palliative radiation therapy.
• Palliative chemotherapy with or without radiation therapy.
• A clinical trial of immune checkpoint inhibitors.
• A clinical trial of new treatment options.

Treatment of HIV and Anal Cancer

In general, treatment for patients who have anal cancer and the human immunodeficiency virus (HIV) is similar to treatment for other patients, and these patients have similar outcomes. However, this treatment can further damage the weakened immune systems of patients who have HIV. Treatment in patients with a history of AIDS-related complications may require lower doses of anticancer drugs and radiation therapy than doses used for patients who do not have HIV.

Treatment of Recurrent Anal Cancer

Treatment of recurrent anal cancer may include the following:

• Radiation therapy and chemotherapy, for recurrence after surgery.
• Surgery, for recurrence after radiation therapy and/or chemotherapy.
• A clinical trial of radiation therapy with chemotherapy and radiosensitizers.
• A clinical trial of chemotherapy options.
• A clinical trial of immune checkpoint inhibitors.