Background The similarity between clinical pictures of pigmented actinic keratosis (PAK) and lentigo maligna (LM) is well known.
Objectives To investigate the frequency of dermatoscopic findings suggestive of LM/lentigo maligna melanoma (LMM) in the other facial pigmented skin lesions (FPSL) and to assess the distinguishing dermoscopic criteria of PAK and LM.
Methods Eighty-nine FPSL were evaluated with conventional dermatoscopy. The lesions showing one or more dermatoscopic features considered as specific patterns for the diagnosis of LM/LMM, mainly slate-grey to black dots and globules, slate-grey areas, annular-granular pattern, asymmetrical pigmented follicular openings, black blotches, rhomboidal structures, hyperpigmented rim of follicular openings, slate-grey streaks and dark streaks, were included in the study selectively.
Results PAK was diagnosed in 67, LM or LMM in 20 and lichen planus-like keratosis in two lesions, histopathologically. Eleven essential dermatoscopic features were observed in facial PAK: slate-grey dots (70%); annular-granular pattern (39%); rhomboidal structures (36%); pseudonetwork (36%); black globules (34%); slate-grey globules (33%); black dots (30%); asymmetrical pigmented follicular openings (25%); hyperpigmented rim of follicular openings (21%); slate-grey areas (18%); and streaks (3%).
Conclusions PAK has a striking similarity to LM/LMM in clinical and dermatoscopic features, thus representing a diagnostic challange. All dermatoscopic findings except black blotches were observed in PAK. As dermatoscopic diagnosis of a pigmented skin lesion cannot be based on the presence of a single criterion, we may conclude that histopathology still remains the gold standard for correct diagnosis.