Counting Your Moles for Melanoma


If you have a lot of moles on your body, you probably don’t feel inclined to count them; you just wish they would go away.  But the moles will not go away and it's necessary to monitor them because they are the number one risk factor for melanoma, the deadliest form of skin cancer. 

You have probably read a lot about sun exposure as a major cause of skin cancer. As for moles...not so much.

But if you’re a person

  • with 100 or more moles,
  • red hair and
  • fair skin, you should be monitoring those moles as well as limiting your time on the beach.
The above three traits often go together, usually in persons of Celtic or other northern European descent.

A study published in Nature Genetics [July, 2009] reported on the discovery of two genes that are implicated in the tendency to have numerous moles as well as the higher risk of melanoma. Having numerous moles is the number one risk factor for melanoma, the authors wrote. And it’s significantly more important than the time you sit or lie with your skin exposed to the sun.

Preventive efforts, they wrote, should be focused on these high-risk individuals and watching for changes in their moles that could be a sign of cancer.

A child with fair skin is highly likely to suffer at least a few sunburns and pick up even more moles and freckles than he already had. If other persons in the immediate family have had melanoma, the risk is even higher.

A mole (the medical term is nevus) is a growth in the skin that is usually harmless. Some babies are born with one or more congenital moles. Generally, speaking, though, moles rarely surface before age 12 but appear in increasing numbers during the teen years on the skin of those who are vulnerable.

About 90 percent of whites and 70 percent of non-whites have at least one mole. The average number per person is about 12.

A person with 12 or more moles with a diameter of a quarter of an inch or greater has a 41-fold increased risk of developing melanoma. Having even five moles that size confers a seven-fold increased risk. And a person with 50 or more smaller moles has a seven-fold higher risk.

Don’t Miss Warning Signs

There are a few signs of imminent melanoma that should be checked out promptly:
  • a new mole, especially one that looks different than the others;
  • an existing mole that has changed or is changing;
  • atypical or dysplastic moles.
Dysplastic moles tend to be relatively large and have uneven or fuzzy borders. They are sometimes hard to distinguish from an early melanoma. And, indeed, some may be early melanomas.

The tendency to have these atypical moles is at least partly genetic, affecting from two to eight percent of Caucasians. Some individuals have 10 or more of these atypical moles, and these individuals are 12 times more likely than others to develop melanoma. If you have even one such mole, your lifetime risk of developing melanoma is 5 to 10 percent.

The melanoma may develop on the dysplastic mole. Or it could develop somewhere else on the body, sometimes in an area that does not get sun exposure like the sole of the foot or the palm of the hand.

About five percent of melanomas start as a lentigo maligna. This is a light brown area on sun-damaged skin–often on the face–that usually appears after age 35. On becoming a melanoma, this spot may darken in color and the borders spread. Eventually, elevation of the surface may occur, indicating a possible melanoma.

Less than one percent of babies are born with a congenital nevus; and, in most cases, it’s just one. A congenital mole tends to be medium to light brown in color and slightly distorts the skin surface. During infancy and childhood, it typically expands in proportion to the growth of the body part where it is located, and it may also change slowly in pigmentation, hair and surface characteristics. Once body growth ends, however, growth and changes in color and surface of the mole should also cease. Any changes at this point should be noted and reported promptly to a physician.

From 3 to 15 percent of melanomas develop in a congenital nevus. Anyone with such a mole has a five percent risk of developing melanoma at some time in life.

Moles are common, and nearly all are harmless. It is important to monitor the number and nature of moles on your body, however, because they represent the number one risk factor for the most dangerous skin cancer.

Other major risks include:

  • having had a prior melanoma;
  • having a parent, sibling or child with a melanoma. This risk is believed to be related to the familial risk of having numerous moles, dysplastic moles and congenital moles.
Individuals who develop dense freckling when their skin is exposed to the sun have an increased risk of melanoma as well as the more common but less dangerous basal cell and squamous cell carcinomas. Sometimes a sun-induced freckle can become a lentigo maligna.

Persons who have a tendency to burn rather than tan also have an increased risk of all skin cancers. Some believe that ultraviolet exposure on fair, sun-sensitive skin causes the proliferation of moles and freckles. And some experts believe that sun exposure, particularly in excess, increases the chance that high-risk moles that are already present might transform into melanoma.

Doctors stress that there is good reason to be sensible about sun exposure and to use sunscreen and a wide-brimmed hat to protect yourself against premature aging, cataracts and all skin cancers, including melanoma.

Particularly if you have a higher than average genetic risk, the most important thing you can do is check your skin regularly–about every month or so. Know the pattern of moles, freckles and other marks or growths on your skin, and be suspicious of any changes or any newcomers.

A normal mole is usually evenly colored–brown, tan or black. It can be round or oval, flat or raised but usually less than a quarter inch in diameter–about the width of a pencil eraser.

The ABCDE rule provides some warning signs. Be suspicious of any mole that is Asymmetrical; has a Border that is irregular, ragged, notched or blurred; has several Colors such as shades of brown or black or patches of pink, red, white or blue; has a Diameter greater than one quarter inch; and is Evolving or changing in size, shape or color.

But don’t depend on your own judgment; when suspicion rises, see your doctor or health care provider.

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