Cutaneous melanomas associated with nevi.

OBJECTIVE To determine the frequency of and the histologic and clinical factors associated with melanoma existing in histologic contiguity with a nevus. DESIGN Pathology reports from melanomas collected from January 1, 1993, to December 31, 1997, were retrospectively reviewed. SETTING Independent, community-based dermatopathology laboratory. PATIENTS A total of 1606 patients with a histologic diagnosis of melanoma. INTERVENTION None. MAIN OUTCOME MEASURES Differences in histologic (subtype, Breslow thickness, and Clark level) and clinical (age, sex, and anatomic location) features between melanomas that are associated and unassociated with a nevus. RESULTS Twenty-six percent of the melanomas reviewed were histologically associated with nevi (dysplastic nevi, 43.0%; and other nevi, 57.0%). Factors that were significantly associated with an increased likelihood of a melanoma being histologically contiguous with a nevus included younger age, superficial spreading subtype, truncal location, Breslow thickness, and Clark level. However, after multivariate analysis, only younger age (odds ratio, 1.27; 95% confidence interval, 1.19-1.37), superficial spreading subtype (odds ratio, 2.96; 95% confidence interval, 2.17-4.02), and truncal location (odds ratio, 3.26; 95% confidence interval, 2.55-4.19) remained significant. CONCLUSIONS Most melanomas were not histologically contiguous with a nevus. Younger age, superficial spreading subtype, and truncal location are independent significant predicators of a melanoma being histologically associated with a nevus.