April 22 (HealthDay News) -- Skin lesions larger than six millimeters in diameter are more likely than smaller lesions to be melanoma skin cancer, a new study suggests.

The finding supports the current widespread use of diameter guidelines to screen for melanoma, researchers say.

This "ABCDE" screening method is based on five features characteristic of melanoma: asymmetry, border irregularity, color variegation, diameter larger than six millimeters, and changes in a lesion.

However, some experts have argued that strict adherence to the diameter guideline will cause doctors to miss smaller melanomas, according to background information in the study.

In this study, researchers at the New York University School of Medicine, New York City, studied more than 1,300 patients undergoing biopsies for 1,657 pigmented skin lesions or markings suggestive of melanoma. Of those lesions, 804 (48.5 percent) were larger than six millimeters in diameter and 138 (8.3 percent) were diagnosed as melanoma.

Invasive melanomas (which have penetrated deeper into the skin) were diagnosed in 13 of 853 lesions (1.5 percent) that were six millimeters or smaller in diameter and in 41 of the 804 (5.1 percent) of lesions that were larger than six millimeters. In situ melanomas (those that remain in the skin's outer layers) were diagnosed in 22 of the 853 (2.6 percent) of lesions six millimeters or smaller and in 62 of the 804 (7.7 percent) of lesions larger than six millimeters.

"With each one-millimeter diameter range from 2.01 to six millimeters, the proportion of melanomas did not vary significantly, remaining stable at 3.6 percent to 4.5 percent," the study authors wrote. "However, we observed a nearly 100-percent increase in the proportion of melanomas when comparing the 5.01- to six-millimeter category (4.3 percent) to the 6.01- to seven-millimeter category (8.3 percent)."

The study was published in the April issue of the journal Archives of Dermatology.

"We recommend that a diameter criterion of larger than six millimeters remain a part of the ABCDE criteria," the researchers concluded. "We do not recommend downward revision of the D criteria 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."

SOURCE: JAMA/Archives journals, news release, April 21, 2008