What is melanoma?

Melanoma is a type of cancer that usually starts in the pigment cells (melanocytes) in the outer layer (epidermis) of the skin. Occasionally it occurs in other parts of the body such as the eye, mouth, or vagina. This information deals only with melanomas of the skin.

Melanomas tend to spread out within the epidermis before moving into the deeper layer of the skin (the dermis). A melanoma which has spread into the dermis is known as an invasive melanoma.

Each year in New Zealand about 1600 people are diagnosed with melanoma. If melanoma is detected early it can nearly always be successfully treated. Melanoma can occur in adults of any age, including young adults. It is the most common cancer in people aged 20-39.

Occasionally it can occur in teenagers. It is almost unheard of in children. However, as people grow older they are more likely to develop melanoma.

What causes melanoma?

The causes of melanoma are not fully understood. However, melanoma is most common in fair-skinned people who have been exposed to large amounts of sunlight.

People exposed to large amounts of sunlight during childhood have an increased chance of developing melanoma as an adult. Serious sunburn, especially when young, may also play a part.

However, melanoma sometimes occurs on areas of the body not normally exposed to the sun, so other factors are involved.

These are not known at present, though the risk of developing melanoma is greater if other members of the family have had melanoma.

People with a fair skin who burn easily are at greatest risk of developing melanoma. It is most common in people with Northern European ancestry.

Melanoma is not common among dark-skinned people, and few Maori, Pacific Island or Asian New Zealanders develop it.

A few people have a large number of abnormal moles called atypical naevi. These moles are usually larger than 6mm, have an irregular shape and are multi-coloured. Atypical naevi are not cancers, and a melanoma does not necessarily start in an atypical mole. However, people with many atypical naevi are more likely to develop melanoma.

How is the diagnosis made?

The first sign of a melanoma is usually a change in a freckle or mole, or a new spot on the skin. A melanoma looks like an unusual freckle with an irregular edge. It may have a variety of colours including brown, black, blue, red and, occasionally, light grey.

An early melanoma is normally flat but it may later become raised. Others signs are a spot, freckle or mole which is itchy or tender, or bleeds or has a crust. Melanomas can occur anywhere on the body, not only in areas that get a lot of sun.

If your doctor suspects you have a melanoma, you will have it removed and sent to a lab for examination under a microscope.

If you have melanoma, the doctor will examine your whole body to see if cancer cells have spread to other areas. Other tests are not usually needed.

There are different types of melanoma, depending on their appearance. The most common type, a superficial spreading melanoma, starts as a flat, freckle-like spot which first spreads out sideways in the skin.

The thickness of a melanoma is measured in millimetres (from the top of the deepest point it has reached). The thinner the melanoma, the better the outlook following treatment. Thicker melanomas are more likely to have complications.

A melanoma is also classed by the level of the skin it has reached. The earliest melanoma, known as Level I, is in the epidermis. Other invasive melanomas are described from Levels II to V, depending on how far they have invaded deeper levels of skin.

Staging refers to how far the cancer has spread to other parts of the body. A Stage I melanoma is an early cancer that is limited to the skin.

Treatment

Surgery is the usual treatment for early melanomas. The extent of surgery depends on the thickness of the melanoma and where it is. Most very thin melanomas do not need extensive surgery. They are usually removed using a local anaesthetic. A small area of normal skin around the melanoma is also removed to make sure that no melanoma cells remain.

For deeper melanomas, a much wider area of skin may need to be removed. You may need a skin graft, which replaces the removed skin with skin taken from another part of your body.

The lymph glands (see glossary) in the area may also be removed. If the melanoma is widespread you may have other forms of treatment.

After your treatment you will need regular check-ups for a period. These checks are important to treat any further problems from the melanoma and to detect any new melanoma early. You will also be encouraged to check your skin regularly.

Your outlook

The very earliest melanomas, confined to the epidermis (Level I) are usually completely curable. The majority of people with a melanoma that has not yet spread beyond the skin (Stage I) have no further trouble.

If you would like information about your own outlook, you need to speak with your doctor who is familiar with your full medical history.

Your feelings

Most people feel overwhelmed when they learn they have cancer. Reactions differ from one person to another. There is no right or wrong way to feel. Your feelings are part of the process of coming to terms with your illness. Family and friends often need as much support and guidance in coping with their feelings as you do.

Talking with family and friends can be helpful. Sometimes it is easier to share your concerns with an outside person, such as a hospital social worker or chaplain. If you're not sure how to contact them, ask your doctor or nurse.

Now or in the future you may like to join a cancer support group, which can offer mutual support and information. To locate a group in your area, contact your local Cancer Society.

Related topics

For more information on cancer, see What is cancer? What causes cancer?

What does that term mean? See Cancer glossary

The New Zealand Guidelines Group and the Society of Dermatologists have published the New Zealand Guidelines for the Management of Malignant Melanoma discussion document on Dermnet www.dermnet.org.nz or www.nzgg.org.nz

Original material provided by the Cancer Society of New Zealand. Edited by everybody.