Malignant melanomas, which account for only 5 percent of all skin cancers, also begin in the outer layer of the skin. One of the main factors for developing melanoma appears to be intense, intermittent exposure to the sun, such as that received by indoor workers who vacation in the sun. Some 50 percent of malignant melanomas develop from pigmented moles, particularly on the upper back and lower legs.

This type of skin cancer is the most deadly, for if it is not treated early, it can invade the inner layer of the skin, the dermis, where blood vessels and the lymph are located. From there it can quickly metastasize. Says oncologist Dr. Larry Nathanson: “The paradox of melanoma is that it is a highly curable disease when it is treated early. On the other hand, when it is metastatic it is relatively resistant to treatment by drugs or radiation.” In fact, only 2 or 3 percent of patients with metastasized melanoma survive for five years. (See the box on page 7 for early warning signs of melanoma.)

Australia has a high rate of skin cancer​—in particular, of melanoma.b This is because the country is populated mainly by fair-skinned Northern European immigrants, the majority of whom live along the coast with its sunny beaches. A study of these immigrants suggested that the earlier in their life they arrived in Australia, the greater their risk of melanoma, bearing out the need to educate about safe sun habits from an early age. The Australian government has mounted an aggressive campaign to educate people about the dangers of the sun, using the slogan “Slip, Slap and Slop,” which stands for “Slip on a T-shirt, Slap on a hat, and Slop on sunscreen.” These moderate changes in life-style are having an impact on the incidence of melanoma among younger age groups in that country.

[Box/Pictures on page 7]

KEY WARNING SIGNS OF MALIGNANT MELANOMA

1. ASYMMETRY. Most early melanomas are asymmetrical (the two sides do not match). Common moles are round and symmetrical.

2. BORDER IRREGULARITY. The borders of early melanomas are often uneven and may have scalloped or notched edges. Common moles have smoother, more even borders.

3. COLOR VARIABILITY. Varied shades of brown, tan, or black are often the first sign of melanoma. As melanomas progress, the colors red, white, and blue may appear. Common moles usually are a single shade of brown.

4. DIAMETER. Larger than common moles, early melanomas tend to grow to a diameter of more than one fourth of an inch [6 mm].

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Source: The Skin Cancer Foundation

Skin samples: Images courtesy of the Skin Cancer Foundation, New York, NY, www.skincancer.org