Melanoma lurks in larger skin lesions, researchers find

April 22, 2008

Skin lesions that are about the size of a pencil eraser are more likely to be melanomas, a deadly form of skin cancer, than smaller moles, according to a new study led by NYU Langone Medical Center researchers.

In a new study published in the April issue of Archives of Dermatology, the NYU researchers confirm that an important warning sign of melanoma — moles that are larger than 6 millimeters, the size of a pencil eraser — is still valid. In recent years, some researchers have argued that strict adherence to this guideline may make clinicians miss smaller melanomas.

“Diameter is a reasonable guideline to pay attention to and we did not see any reason to change it,” says David Polsky, M.D., Ph.D., assistant professor of dermatology and associate director of the Pigmented Lesions Section in the Roland O. Perelman Department of Dermatology at NYU School of Medicine, who led the study.

“Lesions that are smaller than 6 millimeters are unlikely to be melanoma. New and changing lesions are the most concerning, and lesions that are multiple colors are especially suspicious,” says Dr. Polsky.

More than 20 years ago, NYU dermatologists developed a widely used rule, the ABCD acronym, for recognizing growths on the skin that could be early melanomas. They recently added the letter E to the list. The warning signs are: A for asymmetrical lesions; B, lesions with irregular borders; C, lesions with multiple colors; D, for lesions larger than 6 millimeters; and E for evolving lesions that change in size, color, shape or symptoms such as itching over time.

The incidence of melanoma continues to rise. The American Cancer Society estimates that in 2008 there will be 62,480 new cases of melanoma in the United States. About 8,420 people will die of this disease this year. Excessive exposure to sunlight, a fair complexion, a family history of melanoma, and numerous moles, among other factors, place people at higher risk for the disease.

In the new study, Dr. Polsky and his colleagues used a computerized imaging system to measure the lesions in a large database of melanoma cases. They evaluated the lesions of 1,323 patients undergoing biopsies of 1,657 suspicious pigmented lesions. Based on their analysis, 804 or 48.5 percent of the lesions were larger than 6 millimeters in diameter and 138 or 8.3 percent were diagnosed as melanoma. Invasive melanoma, which has penetrated deeper into the skin and is most life threatening, was diagnosed in only 13 or 1.5 percent of 853 lesions that were 6 millimeters or smaller in diameter. By contrast, the invasive type was diagnosed in 41 or 5.1 percent of 804 lesions larger than 6 millimeters.

In situ melanomas, which are less dangerous because they remain in the skin’s outer layers, were diagnosed in 22 or 2.6 percent of 853 lesions 6 millimeters or smaller in diameter and in 62 or 7.7 percent of 804 lesions larger than 6 millimeters.

Source: New York University