Anorectal melanoma

The most common symptom is bleeding from the back passage (anus or rectum).

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 for example, diarrhoea, constipation or leaking (incontinence)
• feeling like you need to poo, even though your bowel is empty.

Other conditions, such as piles (haemorrhoids), can cause some of these symptoms. But if you have any of them, it is important to get them checked by your GP.

If you have symptoms, you will usually begin by seeing your GP, who will examine you. They will feel your tummy (abdomen) and may examine your back passage. This is called a rectal examination.

If your GP is not sure what is causing your symptoms, or if they think your symptoms may be caused by cancer, they will refer you to a 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.
• Some people may also have an internal examination of their vagina. This is because the vagina is very close to the anal canal. But this is usually done during surgery.
• The doctor will also feel your groin to check for swollen lymph nodes. Lymph nodes are part of the body’s immune system which protects you from infection and disease.
• Some people may have an examination under anaesthetic (EUA). Having an anaesthetic means you will not feel anything while the doctor is examining you. Also, you will be relaxed and this can help the doctor do a more detailed examination.
• The doctor will usually want to take a small sample of the affected area. This is called a biopsy. A doctor called a pathologist will examine the biopsy in the laboratory to check for cancer cells.

Waiting for test results can be a difficult time. We have more information that can help.

Your doctor may want you to have some other tests to diagnose anorectal melanoma. These tests can also be used to check whether the cancer has spread. Tests may include:

• CT scan
  A CT scan (computerised tomography) scan uses x-rays to build a three-dimensional (3D) picture of the inside of the body.
• MRI scan
  An MRI scan uses magnetism to build up a detailed picture of areas of your body.
• PET-CT scan
  A PET-CT scan is a combination of a CT scan, and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body.
• Endorectal ultrasound scan (ERUS)
  An endorectal ultrasound scan (ERUS) uses sound waves to make up a picture of the anus and the rectum.
• Ultrasound of the groin
  An ultrasound uses sound waves to make up a picture of an area of the body. You may have this test to look at the groin area.

It may take a few weeks before all your test results are available.

You may have tests on the lymph nodes that are close to the anorectal melanoma. This is to check for any cancer cells in the lymph nodes.

Fine needle aspiration (FNA) of the lymph nodes

You may have a fine needle aspiration (FNA) of the lymph nodes. The doctor puts a fine needle into the lymph node. They then withdraw a sample of cells into a syringe. The cells are sent to a laboratory to be checked for cancer.

Sentinel lymph node biopsy

The sentinel nodes are the first lymph nodes that fluid drains to from anorectal melanoma. A sentinel node biopsy may be done at the same time as the operation to remove the cancer. If your doctor plans to do a SLNB, they will tell you what is involved. This test is not used often. 

We have more about sentinel lymph node biopsy in our skin melanoma information.

A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT).

The MDT should include a surgeon and a cancer doctor with experience in treating anorectal melanoma. The MDT will look at national guidelines to help them plan your treatment.

After the MDT meeting, you will usually see your doctor and specialist nurse. They will talk to you about your treatment plan. Your doctor will explain the different treatments and their side effects. They will also talk to you about things to think about when making treatment decisions.

Your treatment plan will depend on several things including the stage of the cancer and your general health. Your doctor will talk to you about this. Together you can decide on the best treatment plan for you.

The aim of surgery is to remove all of the cancer. Surgery should be done by a surgeon with experience in anorectal melanoma.

Wide local excision

The most common operation for anorectal melanoma is a wide local excision. The surgeon removes the cancer and a small area of healthy tissue around it. This is called the margin. Removing some healthy tissue reduces the risk of any 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 same way as you did before the surgery.

Abdominoperineal resection (APR)

Some people need a bigger operation to remove the cancer. This operation is called an abdominoperineal resection (APR).

The surgeon removes all of the anus and rectum and a small part of your colon. This means poo (stools) and wind will not pass out of the rectum and anus in the usual way. Instead, they will pass out of an opening the surgeon makes through the tummy (abdominal) wall. This is called a stoma. The surgeon may also remove nearby lymph nodes if the cancer has spread there.

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).

Your surgeon and cancer doctor will discuss with you the best operation for you to have and why they recommend it.

Immunotherapy drugs use the body’s immune system to find and attack cancer cells. Immunotherapy may be offered after an operation to increase the chance of being cured of the cancer. Your doctors may recommend immunotherapy instead of an operation.

Radiotherapy uses high-energy rays to treat cancer. It destroys cancer cells in the area where it is given. It may be used after surgery. If anorectal melanoma has spread to other areas of the body, radiotherapy may help control symptoms such as bleeding or pain.

Targeted therapy uses drugs to find and attack cancer cells. There are many different types of targeted therapy. This type of treatment is often not suitable for people with anorectal melanoma.

You may have some treatments as part of a clinical trial.