Benign dermoscopic features in melanoma

Background Various dermoscopic features are usually associated with benign melanocytic lesions. Our objective was to determine frequency and extension of benign dermoscopic features (BDF) in melanoma. Methods Retrospective review of dermoscopic images of a consecutive series of 516 histopathologically proven melanomas collected in 6 years in Graz. Correlation of BDF with mean Breslow thickness, with presence/absence of associated benign nevus component and with the pre-operative clinico-dermoscopic diagnosis, as reported on the original histopathologic reports. Results In addition to melanoma specific criteria, 42% of melanomas showed BDF. In 12.3% cases, the benign features occupied more than the half of the lesion. The BDF typical pigment network, homogeneous pattern and regular globules/cobblestone pattern had the highest frequency. BDF were associated with relatively thinner melanomas (mean Breslow thickness of 0.51 mm). The presence of BDF was observed in 67.1% of histopathologically documented nevus-associated melanoma and in 35.7% of melanoma de novo. A pre-operative clinico-dermoscopic diagnosis of melanoma was achieved in only 54.1% of cases displaying BDF. Conclusion A significant proportion of melanomas may exhibit BDF. Clinicians should be aware of the presence of BDF in melanoma as possible diagnostic pitfall.