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What is Melanoma?

Melanoma is a malignant cancer that's found in the melanocytes of the skin. Melanocytes are pigment cells which cause freckles and moles to appear on the skin. They also produce the bronze skin colour that appears after sun exposure as a sun tan.

Melanoma can develop anywhere on the skin - as well as the eye, soles of the feet, mucous membrane and nervous system, those these types are rare - and spread quickly.

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How the skin works

The skin is the largest organ in the body and does more than determine our appearance. It also helps us regulate our body temperature, shields us from injury and prevents dehydration.

There are two main layers that form the skin: the epidermis and the dermis.

The epidermis is the outer layer and is made up of melanocytes and squamous cells.

The dermis is the inner layer and holds nerves, blood and lymph vessels, sweat glands, and roots of hairs.

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The role of melanocytes

Melanocytes generally fall into two categories: as individual cells spread relatively evenly throughout the body, or grouped together (naevus cells or naevi, sometimes forming what is commonly known as a mole, though this is not the clinical term) at various depths within both layers of the skin.

Melanoma can develop in either category of melanocytes.

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How do I know is a mole is safe?

Most melanomas develop as a new spot on the skin or in a long-standing mole that changes. It is important to get to know your skin well so that you can recognise any changes.

Look for...

  • Increase in size: a mole may expand sideways or become raised. This may be the first sign of a highly dangerous form of melanoma.
  • Change in colour: watch for moles that change colour. Melanomas often develop a blue or black colour. Sometimes many different colours such as red, pink, purple or grey may develop and some areas may become lighter.
  • Change in shape/irregular border: change in shape is usually from an oval or round mole to an irregular (coastline) shape. Most harmless moles have smooth regular borders. Melanomas often have irregular borders.
  • Itch or bleeding: recurring itch may be an important warning sign, but only if there are other changes noticeable in the mole. (Many skin conditions which are not serious are also itchy). If a mole bleeds repeatedly for no apparent reason, you should have it examined by your doctor as soon as possible.
  • Recent appearance: if a mole or freckle has appeared recently on normal looking skin, especially if its colour is uneven or it is growing rapidly, you should show it to your doctor.

It is important to remember if melanoma is identified early, the outcome of treatment for many patients can be a complete recovery.

If it is left untreated, the cancer cells may spread and be carried around the body in blood or lymph vessels. If you have any concerns about a mole do not delay and speak to your doctor as soon as possible, early diagnosis saves lives.

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What will my doctor do?

Most doctors will begin by conducting a physical examination. Your doctor will examine the suspicious spot or mole, as well as other moles on your body. You will also be asked if you or your family have a history of melanoma. If they are not confident that it is safe then they may suggest the following:

A dermoscopy: if your GP or dermatologist has access to a dermoscope, they may refine their diagnosis further before deciding to proceed to a biopsy.

A biopsy is a quick and simple procedure where part or all of the spot is removed and sent to a laboratory. The biopsy may be performed by your GP or you can be referred to a dermatologist or melanoma specialist. The ideal method is an excision biopsy, however in some cases other types of biopsy may be used.

An excision biopsy is a quick and simple procedure that may be done by your GP, dermatologist or a surgeon. You will be given a local anaesthetic injection while the doctor uses a scalpel to cut out the mole and some surrounding tissue. You will then receive a stitch or stitches to help the wound to heal.

The biopsy is sent to pathology for analysis. The next step depends on the pathology's results: if the cells are found to be cancerous, the doctor will stage the melanoma (see below). They may also do other tests to see if the cancer cells have spread. This may include taking more tissue.

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What is meant by staging?

Primary site

Staging is a term used to describe how far the melanoma has spread. Doctors stage melanoma to determine the extent of the spread of the disease and whether or not it has moved from the original site on the skin to the lymph nodes or to other parts of the body.

The first step in staging is to measure how deeply into the skin the cancer cells have grown. This is done by a pathologist once they receive the biopsy from the surgeon. The depth of the melanoma is important because the deeper the cancer cells have grown into the skin, the greater the risk the cancer will come back or spread to the lymph nodes or elsewhere in the body.

If the melanoma cells have not penetrated very deeply into the skin, the removal of the melanoma by the biopsy may be all that is needed and you will not need any further treatment. However, if the tumour has penetrated further into the skin, more tissue may need to be removed from around the melanoma.

Stage I

  • 1A Tumour: <1.00 mm without ulceration; no lymph node involvement, no distant metastases.
  • 1B Tumour: <1.00 mm with ulceration or Clark level IV or V tumour 1.01-2.0 mm without ulceration; no lymph node involvement; no distant metastases.

Stage II

  • IIA Tumour: 1.01-2.0 mm with ulceration; tumour 2.01-4.0mm without ulceration; no lymph node involvement; no distant metastases.
  • IIB Tumour: 2.01-4 mm with ulceration.
  • IIB Tumour: >4.0 mm without ulceration; no lymph node involvement; no distant metastases.
  • IIC Tumour: >4.0 mm with ulceration; no nodal involvement; no distant metastases.

Stage III

  • IIIA: Tumour of any thickness without ulceration with 1 positive lymph node and micrometastasis macrometastasis.
  • IIIB: Tumour of any thickness without ulceration with 2-3 positive lymph nodes and micrometastasis macrometastasis.
  • IIIC: Tumour of any thickness and macrometastasis OR in-transit met(s)/satellite(s) without metastatic lymph nodes, OR 4 or more metastatic lymph nodes, matted lymph nodes or combinations of in-transit met(s)/satellite(s), OR ulcerated melanoma and metastatic lymph node(s).

Stage IV

  • IV: Melanoma that has distant emetasis beyond the original site, this may include other areas of the skin, distant lymph nodes, bone, and other organs including the lungs and brain.

Notes: "Met(s)" refers to metastases. Ulceration is the absence of an intact epidermis overlying a portion of the primary melanoma based on pathologic microscopic observation of the histological sections.

If your melanoma has penetrated further into your skin your doctor may suggest a lymph node biopsy.

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Lymph node biopsy

Lymph nodes are part of the body's immune system. They are located all over the body and act as filters for lymph. Lymph is the fluid that white blood cells are transported in. It also carries oxygen and glucose to the cells in the body. They play an important role in protecting the body from infection as when they "trap" foreign bodies they release white blood cells as part of the body's natural defences. You may be familiar with having swollen or enlarged lymph nodes when you have had an infection. Major lymph node groups are mainly found in the neck, armpit and groin.

Cancer cells may break away from a tumour. They can travel to other areas of the body through either the bloodstream or the lymph system. If the cells travel through the lymph system, they may end up in the lymph nodes. When cancer cells break away from the main tumour and start growing in any other part of the body including the lymph nodes, this is known as a metastasis. Melanoma cells which may have spread from the primary tumour usually occur in the node group nearest to the original skin cancer site.

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