Dermoscopic Differentiation of Facial Lentigo Maligna from Pigmented Actinic Keratosis and Solar Lentigines.

The differential diagnosis of lentigo maligna (LM) from pigmented actinic keratosis (PAK) and solar lentigines (SL) remains a challenge for clinicians, especially in the early stages of LM when there are no distinctive dermoscopic features. Objective of this study was to evaluate the frequencies of selective dermoscopic criteria in LM, PAK, and SL and to find the specific combination of distinguishing dermoscopic criteria for LM. Dermoscopists blinded to histopathological diagnosis evaluated 42 LM, 107 PAK, and 16 SL for the presence of predefined dermoscopic criteria. The differences in the presence of dermoscopic criteria between LM and others were evaluated with the chi-squared test or Fisher's exact test as appropriate. Multivariate logistic regression analysis with the forward conditional stepwise method were performed and odds ratios and corresponding 95% confidence intervals for LM, PAK, and SL were calculated. LM, PAK, and SL showed many common dermoscopic findings. In multivariate logistic regression analysis, darkening at dermoscopic examination (sevenfold), gray circles (sevenfold), target-like pattern (sixfold), gray rhomboids (sixfold), and slate-gray dots/globules (threefold) represented the strongest predictors of LM, while hyperkeratosis (thirteenfold), white circles (twelvefold), and red rhomboids (sixfold) represented the strongest predictors of PAK. The dermoscopic diagnosis of a given lesion should be based on the presence of the combination of specific dermoscopic criteria rather than a single benign or malignant criterion. Our results suggest that the presence of darkening at dermoscopic examination, gray circles, target-like pattern, gray rhomboids, and slate-gray dots/globules should be considered supportive findings for the diagnosis of early LM.