Melanoma

September 17, 2011

Melanoma is a cancer of the skin that occurs when pigmented skin cells begin to grow out of control. Melanoma is often deadly, unlike basal cell and squamous cell skin cancers, which are usually curable. However, if found at an early stage, melanoma can usually be cured. Melanoma often appears as a brown or black spot on the skin, sometimes developing from a mole that has been present for a long time. Melanoma rarely causes obvious symptoms such as pain.

Melanoma begins in the cells that produce skin color. Dark-skinned people are naturally at much lower risk of melanoma compared to fair-skinned individuals. The frequency of malignant melanoma of the skin is increasing faster than any other cancer in the united States. Melanoma is a disease primarily in whites that increases with age.

People with sun-sensitive skin are at increased risk of melanoma. Sun sensitivity refers to the skin’s response to sun exposure and is measured by a variety of markers. These markers include light skin color, light hair color, light eye color, tendency to sunburn, inability to tan, and presence of freckles. Studies have also shown melanoma to be related to an increased number of common moles and, especially, abnormal (dysplastic) moles. Studies of total body mole counts and mole counts on the arms have shown that an increased number of moles is related to a higher risk of developing melanoma. Early sun exposure may cause moles to develop, while other risk factors for melanoma, including adult sun exposure, may help change moles into melanoma.

Ultraviolet (UV) light is the main environmental factor responsible for the development of skin melanoma as well as precursor lesions such as common moles (nevi). UV light is often divided into three regions with UV-A ranging from 320 to 400 nm, UV-B ranging from 290 to 320 nm, and with UV-C ranging from 200 to 290 nm, where visible light spans from 380 to 750 nm.

Sunlight is the major source of UV light. Various types of sun exposure are associated with melanoma, ranging from severe sunburns, occupational activities, vacation sun exposure, beach activities, other recreational activities, cumulative sun exposure, and early migration to sunny places. The most consistent risk factor for melanoma has been sunburns, particularly at young ages. The damage from sunburns can cause an increase in melanoma in the area that was burned, but sunburns also appear to suppress the skin’s immune system. This allows melanomas to occur in nonsun-exposed skin. While dark-skinned people are naturally at lower risk for melanoma, recent studies suggest there is a higher risk of melanoma with prolonged sun exposure after developing a tan. Growing up in a sunny location or spending a large amount of time in the sun, particularly during childhood and adolescence, also appear to be important. Studies show that both intermittent sun exposure (sunburns and sunny vacations) and total sun exposure (over many years) are risk factors for melanoma.

A second source of UV light is from artificial exposures including tanning beds, sunlamps, and tanning booths. Tanning units are available for use at tanning salons where the patron pays for timed “tanning sessions.” Alternatively, entire units may be purchased for home use. Sunlamps, prior to the 1980s, could irradiate only a localized area and emitted primarily UV-B and some UV-C. More recently, tanning beds or standing booths can irradiate nearly 100% of exposed skin, emitting more UV-A and some UV-B. Overall, there appears to be more than a 50% increase in melanoma risk among sunlamp or tanning bed users, with a greater risk associated with more use.

Sunscreens are thought to protect skin from sunburns and many other harmful effects of the sun. Consequently, some professionals suggest that limiting sun exposure through the use of sunscreen can reduce the risk of developing skin cancers by preventing sunburns. However, recent reports have suggested an increased risk of melanoma among sunscreen users. Some researchers think that the increased melanoma risk with sunscreen use may actually be a result of prolonged sun exposure received by those who use sunscreen. However, skin sensitivity to the sun is likely to distort the association between sunscreen use and melanoma, since sun-sensitive individuals are more likely to use sunscreens. Many studies investigating the potential association between sunscreen and melanoma have not accounted for sun sensitivity. When accounting for sun sensitivity, current evidence suggests no association between sunscreen use and melanoma. The lack of a protective effect of sunscreen use may represent the failure of people who use sunscreen to apply enough sunscreen needed for protection, or may reflect a long period of time between protection from sun exposure and development of melanoma. It may be necessary to wait several decades to see if proper application of high-sun-protection-factor (SPF) sunscreen (SPF >15) is truly protective against melanoma.

The use of sunless chemical tanners has increased dramatically in recent years. The tanning effects of sunless tanning products can last 5-7 days; however, the UV protection is shorter lived than the color change. Some dermatologists suggest that using sunless tanning products prior to sun exposure in conjunction with using sunscreens while outdoors may reduce UV damage to the skin, and thereby reduce incidence of skin melanoma. Many dermatologists recommend use of sunless tanning products over intentional sun exposure or tanning bed use for patients who insist on tanning.

The following are important tips to reduce your risk of melanoma: reduce your sun exposure, particularly between 10 AM and 2 PM during Daylight Savings Time; wear protective clothing while in the sun or use a sunscreen with an SPF of greater than 15; when applying sunscreen, use a palm-full of sunscreen and then reapply it every 2 hours; wear protective clothing or use sunscreen even on hazy days or days with light cloud cover; do not use sunscreen to prolong your time in the sun. When there is a strong desire for a tan, use of sunless tanning products combined with sunscreen while in the sun may help prevent melanoma. Avoidance of sun exposure is the only sure way to reduce melanoma risk and aging of the skin. Seeking medical attention for any suspicious moles is important since melanoma can be a deadly disease with few or no symptoms or pain. However, melanoma is also easily curable if identified early and removed.

SEE ALSO: Cancer, Moles, Skin care, Skin disorders

Suggested Reading

  • Langley, R. G., & Sober, A. J. (1997). A clinical review of the evidence for the role of ultraviolet radiation in the etiology of cutaneous melanoma. Cancer Investigation, 15(6) 561-567.
  • Levy, S. B. (2000). Tanning preparations. Dermatologic Clinics, 18(4), 591-596.
  • Westerdahl, J., Ingvar, C., Masback, A., Jonsson, N., & Olsson, H. (2000). Risk of cutaneous malignant melanoma in relation to use of sunbeds: Further evidence for UV-A carcinogenicity. British Journal of Cancer, 82(9), 1593-1599.

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