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A-Z of Skin: Moles & Melanoma


What are Moles?
Moles are overgrowths of the skin's pigment cells (melanocytes). Almost all of us have them. Moles are not normally present at birth but appear in childhood and early teenage years. By the age of fifteen years Australian children have an average of more than 50 moles.

What do Moles Look Like?
Moles are generally medium to dark brown in colour though they range from skin coloured to black. The majority of moles are flat, relatively even in colour and regular in shape. Some moles are raised and these are usually soft to touch and lighter in colour. Moles need to be distinguished from freckles of the kind that occur on the faces of red headed and fair skinned children or on the shoulders following a sunburn. Occasionally moles may develop a white halo around them (halo naevus) and then disappear; this is a natural process and generally harmless.

What Causes Moles?
The number of moles that develop in an individual is determined by both genetic (inherited) factors and by sun exposure. Childhood and early teenage years are the times when sunlight influences the development of new moles most strongly. There is no evidence that hormonal factors (such as puberty) play a role in causing new moles.

How Many Moles Should we Have?
Australians have large numbers of moles by world standards, perhaps because of high sun exposure in childhood. Many Australians have up to 100 moles that are 2mm or more in size by the age of fifteen years. The more moles, the higher the risk of melanoma.

What is the Significance of Having a Large Number of Moles?
Individuals with large numbers of moles (more than 100) are at greater risk of developing melanoma. As the number of moles increases, so does the risk of developing melanoma.

What are Dysplastic Moles?
Dysplastic moles are moles that have evolved some way toward melanoma. Since only very few dysplastic moles actually turn into melanoma they do not need to be removed routinely. If you have multiple dysplastic moles, however, you may need to have regular checks. Your dermatologist may photograph your skin so that changes in your moles can be detected at follow-up visits. Since many melanomas arise as new spots (on previously normal looking skin) it is necessary to observe all of the skin, not only the dysplastic moles.

Dysplastic moles are likely to be large, smudgy around the edges, uneven in colour, irregular in shape and pinkish when compared with most moles

What do Dysplastic Moles Look Like?
If you think you have moles with any of the following 'dysplastic' features, you should discuss your moles with you local doctor.

Dysplastic moles are typically larger than other moles and often have a smudgy, ill-defined border (mole gradually fades into the surrounding skin), uneven colour, irregular shape and some pinkness. Some of these features may also be seen in melanomas. Sometimes it can be hard even for your dermatologist to confidently distinguish a dysplastic mole from melanoma. In that case the mole is removed and sent for pathology.

This man has multiple dysplastic moles and large numbers of moles. He is therefore at increased risk of developing a melanoma

What is a Melonoma?
Melanoma is a cancer of pigment cells (melanocytes) and is a form of skin cancer. Though it is much less common than basal and squamous cell skin cancers, we are more concerned about it because it has greater life-threatening potential. If allowed to grow for a period of time, melanoma will develop the potential to spread via lymphatic and blood vessels to other parts of the body where it may seed and grow (metastasize). Fortunately, unlike cancers that begin in internal organs, melanoma begins on the surface of the skin and is usually brown or black, allowing us to detect its growth earlier and remove it before it becomes life-threatening.

Australia has the highest rate of melanoma occurrence in the world.

What do Melanomas Look Like?
Melanomas usually pass through an initial flat phase which is not significantly life-threatening and is generally curable by having it cut out. Melanomas distinguish themselves from moles by changing. The changes occur in size (enlargement), shape or colour (usually all three). That is, melanomas get larger, more irregular in shape and most often darker and more uneven in colour.

The changes of melanoma are generally detectable over a period of months. Changes that develop over days are almost always due to inflammation or injury and it is appropriate to wait for a week or two to allow sudden changes to go away. If the change fails to revert to normal and continues for more than a month you should see your doctor.

Normal moles usually resemble one another, a different looking mole should be reviewed by your doctor. A new mole after the age of 25 should also be reviewed by your doctor.

Melanomas will generally reach a size that is noticeably larger than most other moles (>6mm) without developing serious life-threatening potential. By this time they will usually show uneven colour and irregular shape. A persistently itchy moles can be another warning sign of a melanoma. Don't wait until your mole becomes elevated or bleeds before seeking medical advice.

These features are summarised in the ABCD rule of melanoma Detection

Asymmetry (If you cut the mole in half the two halves do not look like similar mirror images)
Irregular Border (the outline of the mole is not a smooth oval shape, and may be hazy or blurred)
Diameter - 6mm or larger (melanomas are often larger than other moles, but melanomas can be less than 6mm)
Don't wait until a mole becomes elevated, or bleeds before seeking medical help

Also learn how to systematically check your skin for both melanoma and other skin cancers.

If your medical doctor suspects you may have a melanoma, it should be removed (surgical excision) and sent for pathology.

Unusual Presentations of Melanomas
Some melanomas do not show the features mentioned above. Some are lumpy right from the start. Others have little or no brown pigment and appear as reddish patches or like blood blisters. Not all melanomas are 6mm or greater in size.

Uncommonly they will develop in non-sunexposed areas such as the scalp, palms or soles or under finger or toe nails. These unusual melanomas are generally changing.

What are the Risk Factors for Melanoma?
Growing up in Australia is a risk factor for developing melanoma.
The most important risk factors for melanoma are the number of moles and the presence of dysplastic moles. A previous melanoma, previous severe sunburns, a light complexion and a close family member with melanoma also increase an individuals risk of developing melanoma. Your dermatologist can advise you about your melanoma risk.

How Should I Look for a Melanoma on my Skin?
The kind of checks you should be doing depend on your risk factors. Ask your dermatologist about a surveillance program that is appropriate for you.

Each Australian should be checking his or her skin surface in the mirror, at home, on a regular basis. To do it every new season is an easy way of remembering. It is important to check all of the skin, including the back, backs of the legs and soles of the feet (check your skin). Seek the advice of your doctor if you see a spot that looks different, particularly if it shows any of the changes described above for melanoma.

NEXT: How to protect your own skin and your families skin from skin cancer and melanoma.

Related Pages and Links
Sun Protection
Toddler and Baby Sun Protection
What every Australian Should Know About Skin Cancer
Types of Skin Cancers
Check your skin (for melanoma and other skin cancers)
Skin and Cancer Foundation of Australia


Acknowledgement
This information is based on a publication of the Australasian College of Dermatologists.
Last Modified 1 March, 2001 Dr John R Sullivan / © 2001 Australasian College of Dermatologists