Dermoscopic Analysis of 72 'Atypical' Seborrheic Keratoses

Background Seborrheic keratoses (SK) are easily recognizable by clinical and dermoscopic approach, nevertheless, some lesions act as a simulator of different skin conditions lacking typical clinical and dermoscopic criteria. Objective The aim of our study was to find specific dermoscopic features or a global pattern to improve diagnostic skills for challenging SK. Materials and methods We examined 72 atypical SK excised from September 2014 up to September 2017 by using the 2-step algorithm modified by Malvehy (2002) and Argenziano (2003). Results In our study population, an average of 4.04 out of 15 dermoscopic specific criteria for SK was found (for example, multiple milia-like cysts). Additional criteria not included in 2-step algorithm were blue-whitish veil (found in 3 SK; 4.2%), polymorphous vessels (18 SK; 25%), blotch/globules (6 SK; 8.3%), shiny white streaks (3 lesions; 4.2%). The most represented global patterns were reticular (27 SK; 37.5%) and not specific (15 SK; 20.8%). All lesions exhibited peculiar findings of SK, furthermore elements suggestive for melanocytic lesion were found in 79.2% of all lesions. Comparing the literature and our results, we found 3 significant differences: a) the less prevalence of SK specific criteria in our study population; b) the description of findings usually not related to SK, among which blue-whitish veil, polymorphous vessels, blotch/globules and shiny white streaks, and c) 2 patterns not previously defined represented by “not specific pattern” (20.9% of all lesions examined) and “vascular pattern” (12.5% of all lesions examined) were also described. No specific feature or global pattern, statistically significant for dermoscopic diagnosis of difficult-to-diagnose SK have been found. Conclusion Nevertheless the useful findings, no specific feature or global pattern statistically significant for dermoscopic diagnosis of challenging SK have been found. According to the 2-step algorithm and the dermatoscopic scoring system for melanocytic and not melanocytic lesion, SK with one or more dermatoscopic findings typical of melanocytic lesion should be removed surgically to exclude classic melanoma or melanoma mimicking SK.