Nevus-Associated Melanomas: Clinicopathologic Features

Objectives: The clinical significance of nevus-associated melanoma compared with de novo melanomas remains controversial. It has been suggested that nevus-associated melanomas have a higher Breslow thickness and therefore worse prognosis. Over a 10-year period, this study evaluated the incidence of nevus-associated melanoma and its prognostic significance related to clinicopathologic features. Methods: Cross-sectional study from 1995 through 2004 in a dermatopathology referral center. With available data, we evaluated sex, primary location, histologic subtype, Breslow thickness, Clark level, presence of ulceration, associated lesion, and histologic subtype of the associated lesion. Results: Of 135,653 pathologic records from skin biopsy specimens over a 10-year period, 1,190 melanoma records were selected Nevus-associated melanomas corresponded to 390 (32.8%) melanomas, with thin melanomas having a nevus 1.52 times the association observed with thick melanomas (>1.01 mm; 95% confidence interval, 1.16-1.99; P <.001). Superficial spreading melanoma was the most frequent, while no lentigo maligna melanoma was associated with nevi. The median Breslow thickness of nevus-associated melanomas was lower than that of de novo melanomas. Conclusions: Nevus-associated melanomas, which represent one-third of the melanomas in southeast Brazil, are associated with intermittent sun exposure, superficial spreading melanomas, and lower Breslow thickness. This is one of the largest series describing nevus-associated melanomas in Latin America.