Skin lesions larger than 6 millimeters more likely to be melanomas

Skin lesions larger than 6 millimeters in diameter appear more likely to be melanomas than smaller lesions, according to a report in the April issue of Archives of Dermatology. The findings suggest that the diameter guidelines currently used by dermatologists to screen for melanoma are useful.

Many clinicians use the ABCDE method to screen for melanoma, according to background information in the article. The criteria are evidence-based guidelines that remind physicians of the features characteristic of melanoma-asymmetry, border irregularity, color variegation, diameter larger than 6 millimeters and evolution, or changes in the lesion. However, some researchers argue that strict adherence to the diameter guideline will cause physicians to miss smaller melanomas.

Naheed R. Abbasi, M.P.H., M.D., of the New York University School of Medicine, New York, and colleagues studied 1,323 patients undergoing biopsies of 1,657 pigmented skin lesions or markings suggestive of melanoma. The maximum diameter of each lesion was calculated before biopsy using a computerized skin imaging system.

Of the lesions, 804 (48.5 percent) were larger than 6 millimeters in diameter and 138 (8.3 percent) were diagnosed as melanoma. Invasive melanoma, which has penetrated deeper into the skin, was diagnosed in 13 of 853 lesions (1.5 percent) that were 6 millimeters or smaller in diameter and in 41 of 804 (5.1 percent) lesions that were larger than 6 millimeters in diameter. In situ melanomas, which remain in the skin’s outer layers, were diagnosed in 22 of 853 (2.6 percent) lesions 6 millimeters or smaller in diameter and in 62 of 804 (7.7 percent) lesions larger than 6 millimeters in diameter.

“Within each 1-millimeter diameter range from 2.01 to 6 millimeters, the proportion of melanomas did not vary significantly, remaining stable at 3.6 percent to 4.5 percent,” the authors write. “However, we observed a nearly 100-percent increase in the proportion of melanomas when comparing the 5.01- to 6-millimeter category (4.3 percent) to the 6.01- to 7-millimeter category (8.3 percent).”

“We recommend that a diameter criterion of larger than 6 millimeters remain a part of the ABCDE criteria,” the authors conclude. “We do not recommend downward revision of the D criterion at this time. In the United States, rates of melanoma and nonmelanoma skin cancers have markedly increased, and skin biopsy rates have more than doubled in 20 years. In an era that demands greater data to support clinical decision making, the ABCDE criteria are valuable evidence-based guidelines to aid physicians in decisions regarding the biopsy of pigmented lesions of the skin.”