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The Transformation Rate of Moles (Melanocytic Nevi) Into Cutaneous Melanoma
A Population-Based Estimate
Hensin Tsao, MD, PhD;
Caroline Bevona, MD;
William Goggins, ScD;
Timothy Quinn, MD
Arch Dermatol. 2003;139:282-288.
Background Moles, or melanocytic nevi, are both markers of an increased risk of cutaneous melanoma and direct precursor lesions. Recent strategies to reduce the burden of advanced disease have focused on early detection and ongoing surveillance of moles for malignant degeneration. Inherent in this approach is the notion that moles exhibit a certain risk of transformation into melanoma; however, this risk is unknown.
Objective To estimate the risk of moles transforming into cutaneous melanoma.
Design We first constructed a model of transformation based on the assumption that the minimal number of moles turning into cutaneous melanoma per year is roughly equivalent to the number of melanomas diagnosed each year with associated nevic components. The annual risk was then calculated as the number of mole-associated melanomas diagnosed in 1 year (stratified by 10-year age groups) divided by the number of moles in a the same 10-year age group. We also estimated the cumulative risk during the lifetime of an individual mole by using a modification of the standard life table method.
Results The annual transformation rate of any single mole into melanoma ranges from 0.0005% or less (ie,  1 in 200 000) for both men and women younger than 40 years to 0.003% (about 1 in 33 000) for men older than 60 years. The rate is similar between men and women younger than 40 years but becomes substantially higher for men older than 40 years. For a 20-year-old individual, the lifetime risk of any selected mole transforming into melanoma by age 80 years is approximately 0.03% (1 in 3164) for men and 0.009% (1 in 10 800) for women.
Conclusions The risk of any particular mole becoming melanoma is low, especially in younger individuals. However, since moles can disappear, ones that persist into old age have an increased risk of malignant degeneration. For young people with innumerable moles and no other associated risk factors, systematic excision of benign-appearing lesions would be of limited benefit.
From the Department of Dermatology, Massachusetts General Hospital Melanoma Center, and Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston (Dr Tsao); Division of Dermatology, Department of Medicine, University of Kansas Medical Center, Kansas City (Dr Bevona); Department of Mathematics, Hong Kong Baptist University, Hong Kong, China (Dr Goggins); and Pathology Services Inc, Cambridge, Mass (Dr Quinn). The authors have no relevant financial interest in this article.
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Risk Estimation for Malignant Transformation of Melanocytic Nevi
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Br. J. Ophthalmol. 2003;87:1056-1056.
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Lifetime risk of mole transforming to melanoma is very low
BMJ 2003;327:0-0.
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Transformation of Moles into Melanoma
Journal Watch Dermatology 2003;2003:1-1.
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