Anorectal melanoma

Anorectal melanoma is a rare cancer. It starts in the anus or rectum (back passage).

Symptoms can include:

  • bleeding from the back passage
  • pain, itching or a lump in the back passage
  • a change in your bowel habits
  • feeling the need to go to the toilet often.

It is important to get these symptoms checked by your GP. They will examine you and do some tests.

If you are diagnosed with anorectal melanoma, you will have further tests to find out the size of the cancer, what parts of your body it extends to and if it has spread. These tests help doctors to decide on the best treatment for you.

The main treatment for anorectal melanoma is usually surgery. Sometimes other treatments are used to reduce the chance of the cancer coming back.

It is natural to have lots of different emotions. You may find it helps to talk about your worries with someone.

About anorectal melanoma

Anorectal melanoma is also called anorectal mucosal melanoma (ARMM). It is a rare cancer that starts in the anus or rectum (back passage).

The rectum 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.

A cross-section of the anal canal
A cross-section of the anal canal

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Melanoma develops from cells called melanocytes that give skin its colour. Melanoma usually starts in the skin. But there are also small numbers of melanocytes in the mucosa. The mucosa is a tissue that lines various parts of the body including the anus and rectum. Melanoma that develops in the mucosa is called mucosal melanoma.

We have more information about anal cancer, rectal cancer and melanoma.


Causes of anorectal melanoma

The causes of anorectal melanoma are not known. It can happen at any age but is more likely to affect people over the age of 60. The main cause of skin melanoma is UV light from sunlight and sunbeds. But, this is not a risk factor for anorectal melanoma.


Symptoms of anorectal melanoma

The most common symptom is:

  • bleeding from the back passage

Other possible symptoms include:

  • pain or itching in the back passage
  • a lump in the back passage
  • a lump or swelling in the groin
  • a change in your bowel habits (diarrhoea, constipation or incontinence)
  • feeling the urge to pass a bowel motion, even though the bowel is empty.

These symptoms are usually caused by other conditions. But if you have any of them, it is important to have them checked by your GP.


How anorectal melanoma is diagnosed

You usually start by seeing your GP. They will feel your tummy (abdomen) and 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 is not 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. Women may also have an internal examination of their vagina.

The doctor will also feel your groin to check whether the lymph nodes there are swollen. Lymph nodes are part of the body’s system to protect you from infection and disease. They are usually small, about the size of a baked bean. There are groups of them throughout the body.

The doctor will also arrange for you to have some of the following tests.

Biopsy

This is when the doctor removes a small piece of tissue to be checked for cancer cells.

The doctor may use a thin tube with a light and tiny camera on the end (called a proctoscope). You lie curled on your left side with your knees bent and the doctor gently passes the tube into your back passage. This helps them to see any abnormal areas and take samples (biopsies) from them. You should be able to go home as soon as the test is over. Sometimes, the doctor may arrange to do this test under a general anaesthetic (you will be asleep).


Further tests for anorectal melanoma

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 and its extent. Several tests may be used.


CT (computerised tomography) scan

A CT (computerised tomography) scan uses x-rays to build a three-dimensional picture of the inside of the body. You may be given either a drink or injection of dye. This is to make certain areas of the body show up more clearly. This scan takes around 30 minutes and is painless.

We have more detailed information about having a CT scan.

MRI (magnetic resonance imaging) scan

This scan uses magnetism to build up a detailed picture of areas of the body. You may be given an injection of dye, into a vein, to improve the images from the scan. This test takes about 30 minutes. We have more detailed information about having an MRI scan.

PET-CT scan

This is a CT scan combined with a PET scan. It uses low-dose radioactive sugar to measure the activity of cells in the body. A very small amount of a slightly radioactive sugar is injected into a vein in your hand or arm before you have the scan. Areas of cancer are normally more active than surrounding tissue and absorb more of the sugar, which shows up on the scan.

Ultrasound scan

Ultrasound uses sound waves to make up a picture of a particular area of the body. It is a painless test and only takes a few minutes.

You may have an ultrasound scan of different parts of your body.

  • Rectal ultrasound scan - you lie on your side with your knees bent. A nurse or doctor gently passes a small, lubricated probe, which produces sound waves, into your back passage. The test takes about 30 minutes. 
  • Ultrasound of the groin - once you are in a comfortable position, a gel is spread over the groin. A small device like a microphone, which produces sound waves, is then passed over the groin. This produces a picture on a screen. If the lymph nodes are larger than normal the doctor will do a fine needle aspiration of the node or nodes.

Fine needle aspiration (FNA) of the lymph nodes

This test may be done to check for cancer cells in the lymph nodes. It is a quick, simple test. The doctor puts a fine needle into the lymph node and withdraws a sample of cells into the syringe. The cells are then sent to a laboratory to be checked for signs of cancer.

Someone having a CT scan

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos

Having a CT scan

A radiographer explains how a CT scan works, and Jyoti talks about her experience.

About our cancer information videos


Staging for anorectal melanoma

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 staging systems that may be used to stage anorectal melanoma. One of the most commonly used is a number system called the Ballantyne staging system:

  • Stage 1 – the cancer is only in the anus and rectum. There are no signs that the cancer has spread elsewhere.
  • Stage 2 – the cancer has spread to nearby lymph nodes, such as lymph nodes in the groin.
  • Stage 3 – the cancer has spread to other parts of the body.

Doctors may also use the following terms to describe the stage of the cancer:

  • Early, local or clinically local – the cancer has not spread (stage 1).
  • Regional or locally advanced – the cancer has begun to spread into surrounding tissues or nearby lymph nodes (stage 2).
  • Advanced, widespread or metastatic – the cancer has spread to other parts of the body (stage 3).


Treatment for anorectal melanoma

The main treatment for anorectal melanoma is usually surgery. Sometimes other treatments, such as radiotherapy, chemotherapy or targeted therapy may be 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 several factors including the stage of the cancer and your general health. You and your doctor will decide on the best treatment plan for you.


Surgery for anorectal melanoma

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.


Wide local excision

This is the most common operation for anorectal melanoma. 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.

The anal muscles are not usually affected. This means you should still be able to control your bowel in the normal way after treatment.

Abdominoperineal resection (APR)

Some people need a bigger operation to remove the cancer. Your doctor may suggest this operation if:

  • you had a local excision but some cancer could not be removed or has come back
  • the tumour is in a difficult area to remove with a local excision
  • the tumour cannot be completely removed by a local excision, and involves structures in the anus or rectum that may cause a loss of bowel control (incontinence).

In an APR, the surgeon removes all of the anus and rectum. They may also remove nearby lymph nodes if the cancer has spread there.

Rectal surgery - abdominoperineal resection
Rectal surgery - abdominoperineal resection

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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.

Colostomy bag
Colostomy bag

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Being told you need a stoma can be distressing, but most people find they get used to the stoma over time. You will get support and advice from a stoma nurse in your hospital. We have more information about living with a colostomy.

Lymph node dissection

If an ultrasound scan suggests that melanoma has spread to lymph nodes, the surgeon may remove them as part of the operation. This is called lymph node dissection. There is a risk of leg swelling after lymph nodes are removed from the groin. This is called lymphoedema.


Radiotherapy for anorectal melanoma

Radiotherapy uses high-energy rays to destroy the cancer cells, while doing as little harm as possible to normal cells.

Radiotherapy may be given to the anus and rectum after surgery. Nearby lymph nodes may also be treated. Radiotherapy given to this part of the body is called pelvic radiotherapy. The aim is to reduce the risk of the cancer coming back in that area.

The treatment is given 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 that the rays are aimed at. It does not make you radioactive.

If the cancer has spread to other areas of the body, radiotherapy may be given to a specific area to control symptoms, such as bleeding or pain. In this case, you might only need a few days of treatment or just a single dose.

Pelvic radiotherapy side effects

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.

Some possible side effects are:

  • dry, sore, itchy skin in the area being treated
  • needing to pass urine more often
  • diarrhoea or loose stools
  • tiredness (fatigue).

We have more information about coping with the side effects of pelvic radiotherapy.


Targeted therapies for anorectal melanoma

Targeted therapies are drugs that target the differences between cancer cells and normal cells. There are several targeted therapies used to treat melanoma. These include ipilimumab and imatinib. Some targeted therapy drugs 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 is not possible or if the cancer comes back. This treatment may only be available if you take part in a clinical trial.


Chemotherapy for anorectal melanoma

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 temporarily reduce the number of white cells in your blood. This can 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 tired is another common side effect. It is 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 protein to your diet. Some food supplements can be used to replace meals, and you take others in addition to your normal diet. You can buy some of these food supplements from a chemist or supermarket. Your doctor, nurse or dietitian can also prescribe them for you.

We have more information about coping with the side effects of chemotherapy and about different chemotherapy drugs.


Clinical trials and new treatments for anorectal melanoma

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 will still receive the best standard treatment available.


Follow-up for anorectal melanoma

After your treatment ends, you will have regular check-ups and possibly scans or x-rays. If you have any problems or notice any new symptoms between check-ups, let your doctor know as soon as possible.


Your feelings about anorectal melanoma

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 is 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 is 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 for more information and support. Our online community is also a good place to talk to people who may be in a similar situation.

You may want to contact some other useful organisations:

  • Melanoma UK provides support and information for people with melanoma and their families.
  • Melanoma Focus commissions and funds melanoma research, and provides support and information for patients, carers and healthcare professionals.
  • The Colostomy Association provides support and information for anyone who has, or is due to have, a colostomy.

Living with anal cancer

Tania talks about her experience of living with anal cancer, how she felt after diagnosis and the difficulty she had finding other people who have had rare cancers.

About our cancer information videos

Living with anal cancer

Tania talks about her experience of living with anal cancer, how she felt after diagnosis and the difficulty she had finding other people who have had rare cancers.

About our cancer information videos

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