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Cancer of the anus is rare. The most common type of anal cancer is squamous cell carcinoma. Other rarer types are basal cell carcinoma, adenocarcinoma and melanoma.

The anus

The anus is the name for the muscular opening at the very end of the large bowel.

It is controlled by a ring of muscle called a sphincter that opens and closes to control bowel movements. The area that connects the anus to the rectum is called the anal canal and is around 3–4cm (1–1½in) long.

A cross-section of the anal canal

Causes and possible risk factors of anal cancer

Anal cancer is slightly more common in women than in men. Many factors can increase your risk of developing anal cancer. These include:

Human papilloma virus (HPV)

Anal cancer is more likely to develop in people who’ve had a viral infection called the human papilloma virus (HPV). The risk of having HPV increases with the number of sexual partners you have.

Sexual activity

People who have anal intercourse are more likely to develop anal cancer. This may be because they are more likely to have anal HPV. However, anal cancer can also develop in people who haven’t had anal intercourse or HPV.

Lowered immunity

The immune system is part of the body’s defense against infections and illnesses like cancer. Anal cancer is more common in people who have a lowered immunity, such as people taking medicines to suppress their immune system after an organ transplant or people with conditions such as HIV.


Smoking tobacco increases the risk of developing anal cancer. We have more information about stopping smoking.

Although these factors can increase a person’s risk of anal cancer, many people will not have these risk factors and the cause of their cancer remains unknown.

Signs and symptoms of anal cancer

The most common symptoms of anal cancer include:

  • bleeding from the anus
  • pain, discomfort and itching around the anus
  • small lumps around the anus which may be confused with piles (hemorrhoids)
  • difficulty controlling your bowels (fecal incontinence)
  • discharge of a jelly-like substance from the anus (mucus)
  • ulcers around the anus that can spread to the skin of the buttocks.

How anal cancer is diagnosed

Usually you begin by seeing your PCP who will examine you and refer you to either a surgeon or a specialist in bowel conditions (a gastroenterologist).

At the hospital, the doctor will examine you and ask about your general health and any previous medical problems. They will do some tests before they can make a firm diagnosis of anal cancer.

Rectal examination

This is also sometimes known as a PR examination. A doctor examines your back passage with a gloved finger. Women may also have an internal examination of their vagina, as the vaginal wall is very close to the anal canal.


The doctor will put a thin tube into your back passage to examine the anal canal and rectum. This is called a proctoscopy. A small sample of tissue is taken from the tumor to be examined under a microscope (biopsy). This can be done under local or general anesthetic. Sometimes a biopsy can be taken without needing to use a proctoscope.

If the tests show that you have anal cancer, you will need further tests to find out more about the position of the cancer and to see if it has begun to spread.

CT (computerized tomography) scan

A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of the body. The scan is painless and takes 10-30 minutes. CT scans use small amounts of radiation that are very unlikely to hurt you or anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

You may be given a drink or injection of a dye that allows particular areas to be seen more clearly. For a few minutes, this may make you feel hot all over. If you are allergic to iodine or have asthma you could have a more serious reaction to the injection, so it’s important to let your doctor know beforehand.

MRI (magnetic resonance imaging) scan

This test is similar to a CT scan but uses magnetism, instead of x-rays, to build up a detailed picture of areas of your body. Before the scan you may be asked to complete and sign a checklist. This is to make sure it’s safe for you to have an MRI scan.

Before having the scan, you’ll be asked to remove any metal belongings, including jewelry. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium and can help the images from the scan show up more clearly. During the test you will be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It’s painless but can be slightly uncomfortable, and some people feel a bit claustrophobic during the scan. It’s also noisy, but you’ll be given earplugs or headphones. You’ll be able to hear, and speak to, the person operating the scanner.

PET-CT scan

This is a combination of a PET scan, which uses low-dose radiation to measure the activity of cells in different parts of the body, and a CT scan. PET-CT scans give more detailed information about the part of the body being scanned. They are not always necessary but you can discuss with your doctor whether one would be useful in your case. They are a new type of scan and you may have to travel to a specialist center to have one.

Endoanal ultrasound scan

This uses sound waves to form a picture. A small probe that produces sound waves is passed into the back passage (rectum). This scan can show the size and extent of the tumor. The test is painless and takes about 30 minutes.

Staging and grading of anal cancer


The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the particular type and stage of the cancer helps the doctors to decide on the most appropriate treatment.

Cancer can spread in the body, either in the bloodstream or through the lymphatic system. The lymphatic system is part of the body’s defense against infection and disease. It is made up of a network of lymph nodes connected by fine ducts containing lymph fluid. Your doctors will usually check the nearby lymph nodes when staging your cancer.

Stage 1

The cancer only affects the anus and is smaller than 2cm (¾in) in size. It has not begun to spread into the sphincter muscle.

Stage 2

The cancer is bigger than 2cm (¾in) in size, but hasn’t spread into nearby lymph nodes or to other parts of the body.

Stage 3A

The cancer has spread to the lymph nodes near the rectum, or to nearby organs such as the bladder or vagina.

Stage 3B

The cancer has spread to lymph nodes in the groin and pelvis, or to lymph nodes close to the anus, as well as nearby organs such as the bladder or vagina.

Stage 4

The cancer has spread to lymph nodes in the abdomen or to other parts of the body, such as the liver.

A different staging system called the TNM staging system is sometimes used instead of the number system described above.

  • T describes the size of the tumor and whether it has spread into nearby organs.
  • N describes whether the cancer has spread to the lymph nodes.
  • M describes whether the cancer has spread to another part of the body, such as the liver (secondary or metastatic cancer).

This system is more complex and can give more precise information about the tumor stage.

If the cancer comes back after initial treatment, it is known as recurrent cancer.


Grading refers to the appearance of cancer cells under a microscope and gives an idea of how quickly a cancer may develop. Low-grade means that the cancer cells look very much like normal cells. They’re usually slow-growing and are less likely to spread. In high-grade tumors the cells look very abnormal, are likely to grow more quickly and are more likely to spread.

Treatment for anal cancer

The main type of treatment for anal cancer is a combination of radiotherapy and chemotherapy. The two treatments are normally given at the same time (chemoradiation) but may also be given in sequence, one following the other. Combined treatment is usually very successful. If radiotherapy and chemotherapy are given at the same time, the side effects can be more severe.

Surgery may be used to treat small anal tumors or be used in combination with chemotherapy or radiotherapy for advanced anal cancer.


Before you have any treatment, your doctor will give you full information about what it involves and explain its aims to you. They will usually ask you to sign a form saying that you give permission (consent) for the hospital staff to give you the treatment. No medical treatment can be given without your consent.

Benefits and disadvantages of treatment

Treatment can be given for different reasons and the potential benefits will vary for each person. If you have been offered treatment that aims to cure your cancer, deciding whether to have the treatment may not be difficult. However, if a cure is not possible and the treatment is to control the cancer for a period of time, it may be more difficult to decide whether or not to go ahead.

If you feel that you can’t make a decision about treatment immediately, you can ask for more time to decide.

You are free to choose not to have the treatment. You don’t have to give a reason but it can be helpful to let the staff know your concerns so that they can give you the best advice.


This is the use of high-energy x-rays to destroy cancer cells while doing as little harm as possible to normal cells. Beams are directed at the cancer from outside the body (external radiotherapy) as a series of short, daily treatments using equipment similar to a large x-ray machine. The treatment is often given for a few minutes each weekday for 4-6 weeks.

Possible side effects during radiotherapy treatment

Diarrhea and passing gas

During the course of treatment you may have changes in how your bowel works, such as diarrhea or passing more gas. These can sometimes be reduced by avoiding particular foods. Your doctor or a dietitian at the hospital can give you advice about this.

Effects on the skin

It’s very likely that your skin will be sore in the area being treated – around the anus, and perhaps in the scrotal area for men and in the vulval area for women. This soreness usually starts about 2-3 weeks after treatment begins. The skin may become blistered and sore and the area may be quite painful. You can be prescribed painkillers to help with this.

The hospital staff will keep an eye on the area and will advise you how to look after your skin. It’s important that you only use products they recommend. If it becomes very painful to pass urine, the staff may suggest that you have a fine tube (catheter) put into your bladder to drain the urine. This is then removed once your skin has healed.

Hair loss

It’s common to lose your pubic hair. Hair should grow back after treatment finishes, although the hair loss may be permanent.

Extreme tiredness (fatigue)

Fatigue is a common side effect of radiotherapy for anal cancer.

Vaginal dryness

Women may develop dryness and narrowing of the vagina. Because of this you may need to use a lubricating jelly during sex. You may also be advised to use a vaginal dilator with a lubricating jelly to keep the vaginal walls open and supple. Your doctor or specialist nurse can give you more information about this.

These side effects usually decrease gradually once the treatment has ended but it may take some months for skin changes to go back to normal. A few people find that the way their bowel works is permanently altered, however for most people the change is not usually severe. It can usually be easily managed although you may need to take medication.

It’s important to discuss any problems with your doctor or specialist nurse, as there are often ways to reduce them.

Possible side effects after radiotherapy treatment

Infertility (loss of the ability to have children) If you are concerned about the risk of becoming infertile, it’s important to discuss this with your specialist before starting treatment.


Women who have not been through the menopause may find that treatment brings on an early menopause, which can cause hot flushes and sweats. Your doctor or nurse can give you advice on managing menopausal symptoms.


Men may become unable to have an erection (impotence) after treatment. It’s important to let your doctor know if this happens to you as there are different ways of managing impotence. We discuss some of these in our information about sexuality and cancer.


This is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. The chemotherapy drugs are usually given by injection into a vein (intravenously). Drugs commonly used to treat anal cancer include mitomycin and fluorouracil (5FU). Sometimes a drug called capecitabine, which is taken as a tablet, is used instead of fluorouracil.

Chemotherapy can temporarily reduce the number of normal cells in your blood. When your white blood cell count is low you are more likely to get an infection. You‘ll be given information about this and advised about who to call if you have any problems. During chemotherapy your blood will be tested regularly and, if necessary, you’ll be given antibiotics to treat any infection.

Possible side effects of chemotherapy


If your red blood cell count is low (anemia), you may tire very quickly. You may have blood transfusions if you become anemic. If the number of platelets is low you may bruise more easily.

Nausea and vomiting

You may feel sick (nauseous) or be sick (vomiting).

Hair loss

Some chemotherapy drugs can cause temporary hair loss. Your doctor or nurse will be able to tell you if the drugs you’re having are likely to cause hair loss. They can also give you information about coping with this.

Sore mouth

Chemotherapy drugs may make your mouth sore and cause small mouth ulcers. Regular mouthwashes are important and your nurse will show you how to use these properly.


If you don’t feel like eating meals, you can supplement your diet with nutritious drinks or soups. A wide variety of drinks are available and you can buy them at most chemists. You can ask your doctor to refer you to a dietitian for advice about your diet.


Surgery may be used for small tumors. It can also be used if your treatment doesn’t completely get rid of the cancer, or if there are signs that the cancer has returned. Sometimes it’s used if radiotherapy isn’t appropriate, for example if you’ve had radiotherapy to the area before. Occasionally it’s used to relieve symptoms before treatment with chemoradiation.

Local resection

This may be used for small tumors on the outside of the anus. The operation only removes the area of the anus containing the cancer cells.

The anal sphincter isn’t usually affected, so how the bowel works remains the same for most people. Your doctors may sometimes recommend that you have radiotherapy or chemoradiation after you’ve had surgery.

Abdominoperineal resection

This is the removal of the anus and rectum. The operation requires a permanent colostomy, which involves diverting the open end of the bowel to the surface of the abdomen (tummy area), to allow feces to be passed out of the body into a colostomy bag. The opening on the abdominal wall is known as a stoma.

Although the idea of a colostomy is often frightening and distressing at first, most people find that they adapt over time and can return to their normal activities.

You can get support and advice from the stoma nurse in your hospital. We also have information about having a colostomy.

Surgery to relieve symptoms

Occasionally surgery to form a temporary colostomy may be needed before chemoradiation starts. If the cancer is causing incontinence, a blockage in the bowel or significant pain, a temporary colostomy can sometimes help relieve these symptoms.

After treatment for anal cancer

It’s not unusual to have side effects for a time following treatment for anal cancer. These may include feeling bloated, having wind, diarrhea and occasional incontinence. These side effects can be distressing but are usually temporary and improve over several months. Your doctor, nurse or dietitian will be able to give you advice about how to manage any side effects.

You will be followed up for between 5-10 years. If you have side persistent side effects, you may be referred to another specialist for advice and treatment.

Your feelings about anal cancer

Having investigations and treatment for cancer can be a very stressful experience. You may have many emotions including anxiety, anger and fear. These are all normal reactions and are part of the process many people go through as they try to come to terms with their condition.

Many people find it helpful to talk things over with their doctor or nurse. Close friends and family can also offer support.

Become a Patient

At The Center for Cancer and Blood Disorders, our board-certified physicians provide cancer treatment to more than 12,000 patients annually at our locations in Fort Worth – Central Campus, Fort Worth – Southwest, Arlington, Weatherford, Burleson, Granbury, Mineral Wells, and Stephenville. We offer you the latest advances in chemotherapy, radiation therapy, immunotherapy, hormonal therapy, and biological therapy. We also offer you the opportunity to take advantage of groundbreaking cancer treatment available only through clinical trials and cancer research.


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