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.