NEW YORK (Reuters Health) - Identifying pigmented moles that look different from a person's other moles -- the "ugly duckling sign" -- is a practical way to spot malignant melanoma skin cancer, doctors say.

The ugly duckling model is based on the observation that moles, or "nevi," in the same individual tend to resemble one another and that malignant melanoma often deviates from the individual's mole pattern, "even in those with multiple atypical nevi, Dr. Ashfaq A. Marghoob, of Memorial Sloan-Kettering Cancer Center in New York, and associates explain in the Archives of Dermatology this month.

Marghoob's group studied the ability of 34 adults with varying levels of expertise to identify ugly duckling moles in patients with several atypical moles. The participants were 8 pigmented mole experts, 13 general dermatologists, 5 dermatology nurses, and 8 non-MD medical staff members.

The observers were presented with overview photographs of the back, as well as close-up images of individual moles, from 12 patients who had 5 malignant melanomas, at least 8 atypical moles and 140 benign pigmented moles.

All 5 melanomas and 3 benign moles were perceived as different by at least two thirds of the participants, Marghoob and his associates report.

Identification of the ugly duckling showed good diagnostic accuracy for the detection of malignant melanoma skin cancer, even among non-MDs, the investigators report.

The usefulness of the ugly duckling method in malignant melanoma skin cancer screening by general health care providers and lay persons "should be further assessed," the investigators conclude.

SOURCE: Archives of Dermatology, January 2008.