The role of pattern analysis and the ABCD rule of dermoscopy in the detection of histological atypia in melanocytic naevi

Background Clinical features of melanocytic naevi correlate poorly with the presence, histopathologically, of architectural disorder and cytological a typia, making the detection of histological atypia by means of macroscopic appearance unreliable, Objectives The aim of this study was to investigate the diagnostic effectiv eness of dermoscopy in the non-invasive detection of histological atypia in naevi. Methods Observers blinded for histological diagnosis classified a series of 168 melanocytic naevi as common or atypical on the basis of their clinical features and on their dermoscopic profile. The diagnostic performance of b oth methods compared with the true (histopathological) diagnosis was assess ed, Results Dermoscopy using pattern analysis showed better results than clinic al examination in the non-invasive detection of naevi with architectural di sorder with or without cytological atypia (diagnostic accuracy 45% vs. 28%) . A statistically significant difference in the frequency of dermoscopic pa rameters between atypical and common naevi was found for atypical pigment n etwork (39% vs, 17%, P = 0.001) and dermoscopic regression structures (13% vs, 2%, P = 0.008). Dermoscopic features, which best predicted histological atypia in naevi, were regression structures (white scar-like areas or pepp ering), irregular vascular pattern and grey-blue areas (positive predictive values 83%, 83% and 73%, respectively), In contrast, no statistically sign ificant difference in the mean values of the ABCD score between common and atypical naevi was found. The best diagnostic performance of dermoscopy by means of the ABCD rule (cut-off point of 4.0 of total dermoscopy score) was not dissimilar to that of clinical diagnosis (diagnostic accuracy 30%). Conclusions Dermoscopy by means of pattern analysis enhances the diagnostic , accuracy of dermatologists in the prediction of histological atypia in me lanocytic naevi as compared with clinical examination alone.