Last Updated: 2003-03-24 13:27:24 -0400 (Reuters Health)
NEW YORK (Reuters Health) - The risk of transformation of a given mole into a melanoma is very low, especially among younger individuals, according to a report in the March Archives of Dermatology.
Current surveillance and preventive strategies for melanoma rely on the assumption that moles (melanocytic nevi) transform into melanoma over time, the authors explain, but the rate of this presumed transformation has not been calculated.
Dr. Hensin Tsao from Massachusetts General Hospital in Boston, and associates, therefore, developed a transformation model based on population estimates of cutaneous melanoma incidence and number of moles to calculate the risk of moles transforming into melanoma.
From a community-based dermatology practice's database, the researchers found that 26% of 1615 invasive cutaneous melanomas exhibited unequivocal precursor features, and they applied this percentage to the nationwide number of melanomas. From published figures on mole counts in individuals, they calculated the total number of moles in the US population.
The annual rate of any given mole transforming into melanoma ranged from 1 in 200,000 for patients younger than 40 years to about 1 in 33,000 for men older than 60 years, the authors report. Men and women had similar transformation rates before age 40, but the transformation rate became substantially higher for men after age 40.
The risk of a mole present at age 20 years transforming into melanoma by age 80 years was also higher for men (1 in 3164) than for women (1 in 10,800), the report indicates, and the highest malignancy risk (1 in 2000) was that associated with a mole found on a male patient in his fifth decade of life.
"Given our calculations," the authors conclude, "the overall risk reduction [from] surgical eradication is probably limited, since very few lesions excised would ever have progressed to become cutaneous melanomas. Furthermore, in an effort to detect malignant degeneration within melanocytic nevi, photographic documentation ('mole mapping') of all moles on young, low-risk individuals will probably be associated with high cost and low yield of detection."
Instead, the researchers suggest, "Targeted mapping of older individuals (at least older than 30 years) and patients with factors traditionally associated with an increased cutaneous melanoma risk may be more effective."
Arch Dermatol 2003;139:282-288.