SkinCancerNet Article
Who is Most at Risk for Melanoma?

Researchers have identified a number of risk factors associated with melanoma. These risk factors are grouped into four categories: environmental, genetic, immunosuppressive, and previous melanoma. The most common environmental risk factor is ultraviolet (UV) light emitted by the sun or an artificial tanning device, such as a tanning bed or sun lamp. While the sun is a known cancer-causing agent and accounts for skin cancer development, some melanomas are not sun or UV-light related. Several inherited traits, including a family history of melanoma, fair skin, and atypical moles, increase the risk of developing melanoma.

Most dermatologists believe that these risk factors form a complex inter-relationship; making it difficult to identify any single risk factor as the reason a person develops melanoma. There is one exception — a family history of melanoma. Research shows that when one close blood relative has had melanoma, the risk of developing melanoma increases. That risk rises significantly if two or more blood relatives have had melanoma.

To help you determine your risk factors, this article describes each risk factor and what you should know if it is a personal risk factor. The risk factors are grouped by category:

• Environmental

• Genetic

• Immunosuppressive

• Previous Melanoma

Environmental Risk Factors
Sunlight (solar UV radiation). Overexposure to ultraviolet (UV) radiation from sunlight significantly increases the risk of developing skin cancer, including melanoma. One type of melanoma, lentigo maligna melanoma (LMM), develops in elderly white-skinned people with a history of chronic sun exposure.

The UV risk increases if you have had:

• Chronic (long-term) or frequent exposure to sunlight, whether through an occupation or leisure activities. Many summers spent at outdoor pools, on the golf course, or working in the garden without the benefit of sun protection can be considered “chronic exposure.”

• Periods of intense exposure to the sun. Intense exposure occurs when one spends a lot of time outdoors in the summer or lives in an area that receives high-intensity sun year round, such as Florida, the Caribbean, or northern Australia.

When overexposure to solar radiation is combined with other risk factors, such as a family history or melanoma, fair complexion, or the presence of atypical moles, a complex inter-relationship occurs. For example, fair skin may not pose a risk until exposed to intense solar radiation. UV radiation also may increase the number of acquired pigmented moles and induce atypical moles to develop melanoma.

Everyone should practice sun protection. The American Academy of Dermatology recommends that everyone protect their skin by following these sun protection practices:

1. Avoid deliberate tanning.
   Lying in the sun may feel good, but the end result is premature aging (wrinkles, blotchiness, and sagging skin) as well as a 1 in 5 chance of developing skin cancer. Tanning beds and sunlamps are just as dangerous because they, too, emit enough UV radiation to cause premature aging and skin cancer. If you like the look of a tan, there are plenty of sunless tanning lotions on the market today that create a natural look and do not turn your skin orange.

2. Stay out of the sun between 10:00 a.m. and 4 p.m.
   This is when the sun’s rays are strongest.

3. Seek shade whenever possible.
   Be sure to slip into the shade whenever possible.

4. Use broad-spectrum sunscreen with a Sun Protection Factor (SPF) of 15 or higher. Most people do not apply enough sunscreen to help protect against harmful UV radiation. One ounce, enough to fill a shot glass, is considered the amount needed to cover the exposed areas of the body properly. So when applying sunscreen, remember to apply it liberally. Here are a few more tips for using sunscreen:

• When shopping for sunscreen, buy one that is broad-spectrum. “Broad-spectrum” means that the sunscreen protects against the UVA and UVB rays.

• If you will be in the sun for more than 20 minutes, apply a broad-spectrum sunscreen with an SPF of 15 or higher to all skin that will be exposed. This provides basic year-round protection.

• Don’t forget your ears, nose, neck, hands, and toes. Many skin cancers develop in these areas. Protect your lips, another high-risk area, with lip balm that offers sun protection with an SPF of 15 or higher.

• Sunscreen should not be used to prolong sun exposure – only to avoid sunburn. Some UV light gets through sunscreen.

• Sunscreens should be applied to dry skin 15-30 minutes before going outdoors, even on cloudy days. Be sure to reapply it every two hours.

• Be sure to reapply sunscreen after being in water or sweating.

• Sunscreen does not make sunbathing safe.

5. Cover up when you must be in the sun.
   When you will be out in the sun, be sure to wear protective clothing, such as a shirt, and a wide-brimmed hat. Here’s why:

• Clothing protects your skin from the sun’s harmful rays. The tighter the weave, the more sun protection provided. In fact, clothing plays such an important role in sun protection that clothing designed specifically to protect against the sun as well as laundry additives created to boost clothing’s protective function are available. Your dermatologist may be able to provide you with more information about these products.

• A wide-brimmed hat shades your face and neck from the sun’s rays. Wide-brimmed means the brim extends around the entire hat and shades your face and neck.

6. Wear sunglasses that provide 100% UV protection.
   When buying sunglasses, look for products that provide “100% UV protection.”

Chemical and occupational carcinogens. No chemical or occupational carcinogen has been shown to be a risk factor for melanoma. While some studies indicate increased risk in certain chemical industry occupations, these studies have not been able to separate recreational sun exposure and other melanoma risk factors from occupational exposure to suspected chemicals.

Genetic Risk Factors
Genetic risk factors are believed to most strongly correlate to a person’s risk of developing melanoma. These risk factors include a family history of melanoma; moles; and the color of your skin, hair, and eyes.

Family History of Melanoma. Between 5% and 10% of people who develop melanoma have a close blood relative, such as a parent, brother, sister, child, grandparent, aunt or uncle, who developed melanoma.
Inheriting a tendency to develop melanoma is more complex than inheriting a single "melanoma gene." Research is being conducted to determine exactly how melanoma is inherited. It is now known that when a first-degree blood relative (e.g., parent, child, or sibling) develops melanoma, there is an increased risk for developing melanoma. This risk increases significantly if multiple more-distant relatives also have a history of melanoma.

If family history is a personal risk factor: Anyone with a family history of melanoma should perform regular self-examinations of their skin and be screened by a dermatologist regularly. If self-examination reveals a suspicious lesion, make an appointment to see a dermatologist and let the person scheduling the appointment know why you are making the appointment.

Moles. Several studies have shown an increased risk for melanoma when a person has:

• 50+ moles

• Atypical moles

• Large congenital (present at birth) moles

People with a larger than average number of moles (50 plus) are at greater risk for developing melanoma.

Researchers have also found that one-third of non-familial melanomas develop in atypical moles — what dermatologists call “dysplastic nevi.” A dysplastic nevus is characterized by the ABCDs of Melanoma Detection. It is asymmetrical (if you were to fold the lesion in half, the two parts would not match), borders are poorly defined or irregular, color within mole varies, and the diameter tends to be 6 millimeters (about the size of a pencil eraser) or larger when diagnosed. However, melanomas can be smaller. If you notice a mole different from others, or which changes, itches, or bleeds even if it is smaller than 6 millimeters, you should see a dermatologist.

A study of 716 newly diagnosed melanoma patients found that about half of them had numerous dysplastic nevi. This large-scale study confirmed observations made since 1978 that indicate an association between the presence of numerous dysplastic nevi and an increased risk for melanoma. During the study, researchers calculated a person’s risk based on the type and number of moles present. Their conclusions are shown in Table 1.

Table 1 – Study Found Melanoma Risk Increases
with Type and Number of Moles

It is estimated that between 2% and 4% of white adults have at least one dysplastic nevus. People with dysplastic nevi are likely to have moles on the scalp, pubic area, and breasts. Dysplastic nevi occur with far less frequency in African-Americans and Asians.

A person’s risk for developing melanoma increases significantly when the person has atypical moles and a family history of melanoma. According to the American Cancer Society, “a person with one or more dysplastic nevi and at least 2 close relatives with melanoma has a 50% greater risk of developing melanoma.”

About 3% to 8% of non-familial melanomas develop in a congenital mole. The size of this mole appears to be an important risk factor — the larger the mole, the greater the risk. This does not mean that melanoma never develops in small congenital moles; however, moles known as giant congenital nevi pose significantly greater risk for malignant change — about 15% over a lifetime. A giant congenital nevus is shown in this photo:

Melanoma also can develop in acquired (not present at birth) moles. Approximately 40% of 3-year-old children have at least one acquired mole. About 90% of white adults and 70% of non-white adults have one or more acquired moles.

Since exposure to the sun suppresses the immune system, moles subject to sunburn or repeated sun exposure may be at greatest risk. However, moles also can develop in areas seldom exposed to direct sunlight, such as the buttocks or inside of the thighs. In fact, an acquired nevus does not necessarily have to be exposed to ultraviolet radiation to undergo malignant change.

If moles are a personal risk factor: Anyone who has a large number of moles or atypical moles and has never been screened by a dermatologist should make an appointment to be screened. Dermatologists recommend that anyone diagnosed with atypical moles perform regular self-examinations and be examined once every 6 months.

Color of skin, hair, and eyes. The color of a person’s skin, hair, and eyes is clearly linked to the risk of developing melanoma. Characteristics of light pigmentation that increase the risk of developing melanoma are:

• Fair skin

• Blond or red hair

• Blue, green, or gray eyes

• Sensitivity to ultraviolet radiation (likely to burn rather than tan with initial and repeated exposure to sunlight)

• Tendency to freckle or form pigmented moles with sun exposure

If you tan poorly, do not tan at all, or tend to form freckles and pigmented moles with sun exposure, you have a 2-to 3-fold increased risk of developing melanoma.

It is important to know that melanoma develops in all races. While there is a 20-fold decreased risk in dark-skinned individuals with no predisposing family history of melanoma, melanoma does occur. One type of melanoma, acral lentiginous melanoma (ALM), accounts for 50% of all melanomas that arise in dark skin. Some consider ALM a “hidden” melanoma because it develops in places not easily examined or not thought necessary to examine. ALM is found on the palms and soles; underneath nails; and on mucous membranes, such as those that line the mouth, nose, and anus. In its early stages, ALM is often overlooked because it looks like a bruise or nail streak.

If light pigmentation is a personal risk factor: Anyone with light pigmentation is strongly urged to follow sun-protection practices and perform regular self-examinations.

Xeroderma pigmentosum. Certain inherited skin conditions, such as xeroderma pigmentosum, are associated with an increased risk for melanoma. Xeroderma pigmentosum is an extremely rare genetic disorder caused by a defect in the enzyme that repairs damage to DNA, making the person unable to repair ultraviolet B-induced DNA damage. This increases the risk for both melanoma and nonmelanoma skin cancer. People with xeroderma pigmentosum are extremely sensitivite to ultraviolet light.

If xeroderma pigmentosum is a personal risk factor: Anyone with xeroderma pigmentosum should be under the care of a dermatologist.

Immunosuppressive Risk Factors
Suppressing the immune system limits the body’s ability to recognize cancer cells and eliminate them. Research shows that immunosuppression (suppression of the immune system) is associated with a 4-to 5-fold increased risk of developing melanoma. The risk increases if the person has one or more atypical moles or has already had melanoma.

Diseases that suppress the immune system and may increase the risk of developing melanoma include acquired immunodeficiency syndrome (AIDS) and some lymphomas. Medication that retards or prevents organ rejection after a transplant also increases the risk of developing melanoma because such medications suppress the immune system.

If immunosuppression is a personal risk factor: Anyone with this risk factor should be under the care of a dermatologist because immunosuppression greatly increases one’s risk of developing skin cancer.

Previous Melanoma: A Risk Factor
Between 5 and 10% of people who develop one melanoma will develop another independent melanoma.

If previous melanoma is a personal risk factor: Anyone who has had melanoma should perform self-examinations as recommended by their dermatologist, keep all appointments for screenings, and practice sun-protection practices.

Who’s most at risk?
Melanoma’s many risk factors form a complex inter-relationship. Those most at risk tend to have one or more of the genetic risk factors described above. When genetic risks factors are combined with other risk factors, such as overexposure to sunlight or immunosuppression, the potential risk rises.

References:
Johnson, TM et al. “Multiple primary melanomas.” Journal of the American Academy of Dermatology. 1998;39(3):422-7

Tucker MA et al. “Clinically recognized dysplastic nevi. A central risk factor for cutaneous melanoma.” Journal of the American Medical Association, 1997; 277:1439-44.

An educational program brought to you by the American Academy of Dermatology.