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.