Dermoscopic features of naevus-associated melanoma.

Little is currently known about the relationship between melanocytic naevi and melanoma in terms of neoplastic progression. At histological examination, remnants of a pre-existing melanocytic naevus adjoining a melanoma are seen in 20-30% of cases. This study investigated dermoscopic features of 108 naevus-associated melanomas, identified on the basis of histological classification, consecutively observed at a University Department. Because of the risk of misclassification due to destruction of naevus remnants in thick tumours, only lesions of < 1 mm Breslow thickness were considered. We found naevus-associated melanomas showing atypical pigment networks and regression patterns more frequently than de novo melanomas, while irregular blotches and atypical vascular patterns were found less frequently. Dermatologists should be aware that dermoscopic features of melanoma differ according to the histogenesis of the lesion. Atypical pigment networks and regression patterns are the most useful dermoscopic criteria suggested to make a diagnosis of naevus-associated melanoma.