Background The parallel ridge pattern (PRP) is considered the dermoscopic hallmark of acral melanoma (AM). However, it was recently shown that approximately one-third of AMs do not display a PRP dermoscopically, rendering their detection more troublesome. Objectives To investigate the diagnostic accuracy of dermoscopic criteria for the diagnosis of AM. Methods Dermoscopic images of consecutive cases of histopathologically diagnosed AMs and acral naevi with histopathological diagnosis or with at least 1 year of follow-up were evaluated by three independent investigators for the presence of predefined criteria. Crude and adjusted odds ratios and their corresponding 95% confidence intervals were calculated by univariate and multivariate logistic regression, respectively. Receiver operating characteristic curves were used to choose among competing classification schemes. Results In total 603 lesions (472 naevi and 131 AMs) were included in the study. A scoring system (named BRAAFF) composed of six variables was associated with optimal area under the curve and sensitivity for the diagnosis of AM. This method includes four positive (irregular blotches, ridge pattern, asymmetry of structures and asymmetry of colours) and two negative predictors (furrow pattern and fibrillar pattern). Conclusions The BRAAFF checklist significantly improves the diagnostic accuracy of dermoscopy for the diagnosis of AM.
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