A Case of Dysplastic Nevus Evolving into Melanoma In Situ

Abstract

A recent deep sequencing study of primary melanomas and their adjacent lesions has identified an intermediate category of melanocytic neoplasia during melanoma progression, characterized by the presence of more than one pathogenic mutation and distinctive histological features, including so-called dysplastic nevus. We report a case of such intermediate melanocytic lesion on the back of a 50-year-old woman. She had a small melanotic macule on her back since early childhood, which had gradually enlarged in the last 10 years. Examination revealed a brownish-black, bell-shaped plaque on the back 15×14 mm in size, with color variegation and a partial irregular, blurred margin. The histopathology showed marked proliferation of melanocytes with slight nuclear atypia present in both basal and mid epidermal layers in continuation with junctional dysplastic nevus. BRAF gene mutation analysis revealed the V600K mutation. We diagnosed this case as a dysplastic nevus evolving into melanoma in situ.