Anorectal melanoma is a rare cancer that starts in the anus and/or rectum (back passage). Although melanoma is a cancer that usually starts in the skin, it can occasionally develop in other parts of the body.
We hope this information answers your questions. If you have any further questions, you can ask your doctor or nurse at the hospital where you are having your treatment. You may also find our information on anal cancer helpful. This covers tests, treatment and side effects in more detail. If you have any questions, contact our cancer support specialists free on 0808 808 00 00, Monday–Friday, 9am–8pm. Or you can order information online at be.macmillan.org.uk.
What is anorectal melanoma?
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Anorectal melanoma starts in the anus and/or rectum. The anus and rectum are parts of the digestive system. The rectum (back passage) is the last section of the large bowel. The anus is the ring of muscle below the rectum. It controls when bowel motions leave your body.
Melanoma develops from cells called melanocytes that give our skin its colour. Melanoma usually develops in the skin. But because there are melanocytes in different parts of the body, it can occasionally start in other areas, such as the lining of the anus or rectum.
Causes of anorectal melanoma
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The cause of anorectal melanoma is not known. The main risk factor for developing skin melanoma is exposure to ultraviolet (UV) radiation from sunlight, sunbeds or sunlamps. But there doesn't seem to be any link between the risk factors for skin melanoma and anorectal melanoma.
Symptoms of anorectal melanoma
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Symptoms may include:
bleeding from the back passage
pain, itching or a lump in the back passage
a change in your bowel habits (diarrhoea or constipation)
feeling you need to go to the toilet often, even though your bowel is empty.
These symptoms can be caused by other conditions, but it is very important to have them checked by your GP.
How anorectal melanoma is diagnosed
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You usually start by seeing your GP. They will feel your tummy (abdomen) and they may examine your back passage. This is called a rectal examination. To do this, your GP gently places a gloved finger into your back passage to feel for any lumps or swellings. If you find the examination painful, tell them.
If your GP isn’t sure what the problem is, or thinks your symptoms could be caused by cancer, they will refer you to a hospital specialist.
At the hospital, the specialist doctor will ask you about your symptoms and general health. They will also examine you. You will have another rectal examination. The doctor will also feel your groin to check whether any lymph nodes (sometimes called glands) are swollen. Women may also have an internal examination of their vagina.
You will then have some of the following tests.
This is when the doctor removes a small piece of tissue or cells. A pathologist (doctor who specialises in analysing cells) examines the tissue or cells under a microscope to look for cancer cells. A biopsy can be taken in different ways.
The doctor may put a thin tube called a proctoscope into your back passage to examine the anal canal and rectum. You’ll have this test in the hospital outpatients department or on a ward. You will be asked to lie curled on your left side while the doctor gently passes a tube into your back passage. The doctor can see any abnormal areas by using a tiny light and camera on the end of the tube. If needed, they can take a small biopsy. You should be able to go home as soon as the test is over.
This test can be uncomfortable or painful for some people. The doctor may arrange to examine the area more closely and take biopsies under an anaesthetic.
There are other tests that may be used to diagnose anorectal melanoma. These tests can also be used to check whether the cancer has spread. Several tests may be used.
CT (computerised 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. It uses a small amount of radiation, which is very unlikely to harm you and will not harm 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, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It's important to let your doctor know if you’re allergic to iodine or have asthma, because you could have a more serious reaction to the injection.
MRI (magnetic resonance imaging) scan
This test uses magnetism to build up a detailed picture of areas of your body.
You may be asked to complete and sign a checklist to make sure it’s safe for you to have an MRI scan. Before the scan, you’ll be asked to remove any metal belongings, including jewellery. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium. It can help the images from the scan to show up more clearly. During the test you'll 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. It’s also noisy, but you’ll be given earplugs or headphones.
Anal ultrasound scan
This test uses soundwaves to build up a picture of the anus and rectum on a computer screen. For the ultrasound, you lie on your side while a nurse or doctor gently passes a small, lubricated probe into your back passage. The test takes about 30 minutes and is usually painless.
Fine needle aspiration (FNA) of the lymph nodes
You may have this test if the lymph nodes in your groin don’t feel normal or don’t look normal on a scan An FNA checks whether there are any cancer cells in the lymph nodes.
The lymph nodes are part of your body’s system to protect you from infection and disease. Lymph nodes are small and bean-shaped. They filter out bacteria (germs) and disease.
The doctor passes a fine needle into the lymph node and withdraws (aspirates) some cells into a syringe. This might feel a little uncomfortable, but it’s very quick. You don’t usually need a local anaesthetic to numb the area. You might have a tummy (abdominal) ultrasound scan at the same time to help guide the needle.
After the test, a doctor will examine the sample under a microscope to check for cancer cells.
Staging for anorectal melanoma
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The stage of a cancer describes its size and whether it has spread. Knowing the stage of the cancer helps the doctors decide on the best treatment for you.
There are different types of staging system used for different cancers. Because anorectal melanoma is rare, there isn’t a standard staging system used for it. However, your doctor might use a number staging system to describe the cancer.
There are usually three or four number stages. Stage 1 describes early-stage cancer, when it is small and hasn’t spread. Stage 4 describes cancer that has spread to other parts of the body. Stage 2 and stage 3 are between these stages.
Your doctor might also use these words to describe a stage:
Early or loca’ – if the cancer hasn't spread.
Regional or locally advanced – if it has begun to spread into surrounding tissues or nearby lymph nodes.
Advanced or widespread – if it has spread to other parts of the body.
Treatment for anorectal melanoma
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The main treatment for anorectal melanoma is usually surgery. Sometimes other treatments, such as radiotherapy and chemotherapy, are given to reduce the risk of the cancer coming back after surgery. Treatments are also given to manage the symptoms of cancer that has spread.
Your treatment plan will depend on the stage of the cancer and your general health. You and your doctor will decide on the best treatment plan for you.
There are two types of operation used to treat anorectal melanoma. The aim is to remove all of the cancer, or as much of it as possible. The operation you have will depend on the stage of the cancer.
During this operation, the surgeon removes the tumour and a small area (margin) of normal-looking tissue all around the tumour. This reduces the risk of cancer cells being left behind.
This is the most common operation for anorectal melanoma. Because the anal muscles aren’t usually damaged during surgery, you should still be able to control your bowel in the normal way after treatment.
Abdominoperineal (AP) excision
Some people need a bigger operation to remove the cancer. Your doctor may talk to you about an AP excision if:
you had a local excision but some cancer couldn’t be removed or has come back
the tumour is in a difficult area to remove with a local excision.
In an AP excision, the surgeon removes all of the anus and rectum. They may also remove nearby lymph nodes if the cancer has spread there. The surgeon closes the hole where the anus was. They make a cut on your tummy (abdomen) and join the end of your bowel to this opening. This is called a colostomy. After the operation, your bowel motions come through this opening (stoma) instead of your back passage. You wear a bag over the stoma to collect the bowel motions.
Being told you need a stoma is often frightening and distressing at first, but most people find they get used to it over time. You will get support and advice from a stoma nurse in your hospital. We can send you more information about living with a colostomy.
Sentinel lymph node biopsy
Your surgeon may talk to you about having a sentinel lymph node biopsy at the same time as your surgery. This test examines nearby lymph nodes for signs of cancer that might be too small to show up on a scan.
The surgeon injects a tiny amount of radioactive liquid and/or blue dye around the area of the tumour. Then they scan the closest lymph nodes to see which one gets the radioactive liquid and/or blue dye first. The surgeon removes this first lymph node (the sentinel node), to test it for cancer cells.
If the sentinel node doesn't contain cancer cells, it is less likely that the other lymph nodes in the area have been affected by the cancer. If the sentinel lymph node does contains cancer cells, the surgeon will usually remove other lymph nodes in the area.
Radiotherapy uses high-energy rays to destroy the cancer cells, while doing as little harm as possible to normal cells. You have treatment as a series of short, daily sessions (called fractions) over a few weeks. You have treatment from a machine similar to a large x-ray machine. Radiotherapy only treats the area of the body the rays are aimed at. It does not make you radioactive.
Radiotherapy may be given after surgery to reduce the risk of the cancer coming back. In this situation, the lymph nodes in the abdomen and groin can also be treated. Some people are given chemotherapy at the same time. This is called chemoradiation. Having both treatments together is more effective than having one of the treatments on its own. However, the side effects are also worse during chemoradiation. It is important that you are well enough to cope with having both treatments together.
Radiotherapy may also be given to control symptoms such as pain if the cancer has spread to other areas of the body. In this case you might only need a few days of treatment or even just a single dose.
Side effects of radiotherapy to the anorectal area
You may have side effects during your treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your radiotherapy team will let you know what to expect. Tell them about any side effects you have. There are often things that can help.
Radiotherapy to the anorectal area is likely to cause problems with your bowels, such as diarrhoea or passing more wind. Your doctor can prescribe drugs to help with this. Your nurse, radiographer or a dietitian may give you advice about changes to your diet that might help.
Your radiotherapy team will also give you advice about looking after your skin during treatment. It’s common to have a skin reaction in the area being treated. The skin around the anus and in the groin can become sore, red and may become blistered. This usually starts about 2–3 weeks after treatment starts. It may last for 3-4 weeks after treatment ends. Let your radiotherapy team know if your skin becomes sore. They may prescribe creams and painkillers to help.
Radiotherapy to the anorectal area can also irritate your bladder. You may feel as though you want to pass urine often and have a burning sensation when you pass urine. It helps to drink plenty of water and other fluids. Your doctor can prescribe medicine to make it more comfortable to pass urine.
Sometimes radiotherapy to the anorectal area causes long-term effects. These aren’t common, but they can happen months or even years after treatment. A small number of people find their bowel function is permanently changed.
We have more information about pelvic radiotherapy and coping with side effects.
Dr Vincent Khoo explains what to expect from radiotherapy.
Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells.
You may have chemotherapy if surgery isn't possible or if the cancer comes back. You may have chemoradiation to reduce the risk of the cancer returning after surgery.
Side effects of chemotherapy
The side effects depend on the drug or combination of drugs you are given. Your doctor or nurse will explain any treatment you are offered and what to expect. During treatment, let them know about any side effects. They can often prescribe drugs to reduce these.
The most common chemotherapy drug used to treat anorectal melanoma is dacarbazine (also known as DTIC). This is usually given by injection into a vein (intravenously) once every three weeks for up to six doses.
Chemotherapy can reduce the number of white cells in your blood. During treatment, this will make you more likely to get an infection. Your doctor or nurse will advise you on what to do if this happens.
Chemotherapy can also make you feel sick (nausea) or possibly be sick (vomit). Your doctor will prescribe anti-sickness (anti-emetic) drugs to help control this.
Feeling very tired is another common side effect. It’s often worse towards the end of treatment and for some weeks after. Try to pace yourself and get as much rest as you need. It helps to balance this with taking some gentle exercise, such as short walks.
Some chemotherapy drugs can also make your mouth sore. Your nurse can give you more information about looking after your mouth during treatment.
If you find it hard to eat and drink because of any side effects, let your doctor or nurse know. They can give you advice and medications to help. They may refer you to a dietitian for more advice. You may need to take food supplements to add extra energy and/or protein to your diet. Some food supplements can be used to replace meals, and you take others in addition to your normal diet. A few of these food supplements are available directly from your chemist or the supermarket. But your doctor, nurse or dietitian can also prescribe them for you.
We can send you more information about coping with the side effects of chemotherapy and about different chemotherapy drugs.
Targeted therapies are drugs that target the differences between cancer cells and normal cells. There are several targeted therapies used to treat melanoma. Some of these only work if the cancer has changes in genes called BRAF and c-KIT.
Your doctor may talk to you about this type of treatment if surgery isn't possible or if the cancer returns. This treatment may only be available if you take part in a clinical trial.
Clinical trials and new treatments
Cancer research trials are carried out to try to find new and better treatments for cancer. Trials that are carried out on patients are known as clinical trials.
Research into treatments for anorectal melanoma is ongoing and advances are being made. But because anorectal melanoma is rare, there may not always be a relevant trial in progress.
If there is a relevant trial in progress, you may be asked to take part. Your doctor will discuss the treatment with you so that you have a full understanding of the trial and what it means to take part. You may decide not to take part, or to withdraw from a trial at any stage. In this case, you'll still receive the best standard treatment available.
After your treatment is completed, you will have regular check-ups and possibly scans or x-rays. You may continue to have these tests for several years. If you have any problems or notice any new symptoms between check-ups, let your doctor know as soon as possible.
You may have many different emotions, from shock and disbelief to fear and anger. At times, these feelings can be overwhelming and hard to control. But they are natural and it's important to be able to express them.
Everyone has their own way of coping. Some people find it helps to talk to family or friends, while others get help from people outside their situation. Sometimes it’s helpful to share your experiences at a local cancer support group. Some people prefer to keep their feelings to themselves. There is no right or wrong way to cope, but help is available if you need it.
You may want to contact our cancer support specialists free on 0808 808 00 00, Monday–Friday, 9am–8pm for more information and support. The organisations listed below may also be helpful. Our online community is a good place to talk to people who may be in a similar situation.
The Colostomy Association provides support and information for anyone who has, or is due to have, a colostomy.
Call 0800 328 4257 (24 hours a day, 7 days a week) or email firstname.lastname@example.org
The Rarer Cancers Foundation provides guidance, information and support for people affected by rare types of cancer.
Call 0800 334 5551 or email email@example.com
The information in this section has been produced in accordance with the following sources and guidelines:
The Association of Coloproctology of Great Britain and Ireland. Guidelines for the management of colorectal cancer. (accessed August 2014).
The Association of Coloproctology of Great Britain and Ireland. Position statement for management of anal cancer. Colorectal Disease. 13: 44-52. 2011.
Australian Cancer Network Melanoma Guidelines Revision Working Party. Clinical practice guidelines for the management of melanoma in Australia and New Zealand. (accessed August 2014).
Falch C, et al. Anorectal malignant melanoma: extensive 45-year review and proposal for a novel staging classification. Journal of the American College of Surgeons. 217: (2) 324-335. 2013.
Kim K, et al. Biochemotherapy in patients with metastatic anorectal mucosal melanoma. Cancer. 100: (7) 1478–1483. 2004.
Meguerditchian A, et al. Anorectal melanoma: diagnosis and treatment. Diseases of the Colon and Rectum. 2011. 54: (5) 638-644.
Tacastacas JD, et al. Update on primary mucosal melanoma. Journal of American Academic Dermatology. 71: (2) 366-375. 2014.
If you’d like further information on the sources we use, please feel free to contact us.
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