Key dermoscopic signs in the diagnosis and progression of extrafacial lentigo maligna: Evaluation of a series of 41 cases

Background/objectives Lentigo maligna is usually located on the face. Extrafacial lentigo maligna is less common, and diagnosis of early forms is very difficult. Confocal microscopy of facial and extrafacial lentigo maligna shares the same features (abundant dendritic cells and generalised atypical junctional thickenings) and helps us to identify the dermoscopic features of extrafacial lentigo maligna. Methods We analysed dermoscopic and clinical features of 41 lesions diagnosed by confocal microscopy of extrafacial lentigo maligna confirmed on histology to identify dermoscopic signs of early lesions. Results Erased areas on dermoscopy were the clue to diagnose early lesions. At the borders of these areas, very small, round or triangular structures were found. At the lesion periphery, dermoscopy revealed a fine reticular pattern that helped to identify them as a melanocytic lesion. A progressive increase of the number and size of erased areas was accompanied by the appearance of various angulated structures around them (angulated lines, zig-zag structures or polygonal structures). Analysis of invasive lesions revealed very large erased areas containing white lines and atypical vascularisation. Conclusions We have identified the dermoscopic early features and signs of progression by examining the dermoscopic and reflectance confocal microscopy findings of early and invasive extrafacial lentigo maligna.