Dermoscopic clues to differentiate facial lentigo maligna from pigmented actinic keratosis

A. Lallas, P. Tschandl, A. Kyrgidis, W. Stolz, H. Rabinovitz, A. Cameron, J.Y. Gourhant, J. Giacomel, H. Kittler, J. Muir, G. Argenziano, R. Hofmann‐Wellenhof, I. Zalaudek

The limitations of dermoscopy to accurately differentiate between pigmented lentigo maligna (LM) and pigmented actinic keratosis (PAK) might be related to the fact that most studies have focused on pigmented criteria only, without considering additional recognizable features. To investigate the diagnostic accuracy of established dermoscopic criteria for pigmented LM and PAK, but including in the evaluation features previously associated with non-pigmented facial AK. Retrospectively enrolled cases of histopathologically diagnosed LM, PAK and solar lentigo/early seborrheic keratosis (SL/SK) were dermoscopically evaluated for the presence of pre-defined criteria. Univariate and multivariate regression analyses were performed and ROC curves were used. The study sample consisted of 70 LM, 56 PAK and 18 SL/SK. In a multivariate analysis, the most potent predictors of LM were grey rhomboids (6-fold increased probability of LM), non-evident follicles (4-fold) and intense pigmentation (2-fold). In contrast, white circles, scales and red colour were significantly correlated with PAK, posing a 14-fold, 8-fold and 4-fold probability for PAK, respectively. The absence of evident follicles represented also a frequent LM criterion, characterizing 72% of LM. White and evident follicles, scales and red colour represent significant diagnostic clues for PAK. Instead, intense pigmentation and gray rhomboidal lines appear highly suggestive of LM. This article is protected by copyright. All rights reserved.