Dermoscopy of lentigo maligna melanoma: report of 125 cases.

Background: Lentigo maligna melanoma (LMM) is the most common subtype of melanoma on the face. Its presentation may be quite subtle, particularly in early stages, and delayed diagnosis is common. Few dermoscopic studies have been performed and the main dermoscopic features of LMM were defined by Stolz and coworkers in 2000.

Objectives: To investigate classical as well as new dermoscopic features in a large series of LMM in a white-skinned population, in order to evaluate their diagnostic value.

Methods: One hundred and twenty-five consecutive histopathology-proven LMMs were analysed retrospectively based on medical records, clinical and dermoscopic photographs by three independent observers for the presence of 19 predefined criteria.

Results: At least one of the classical Stolz criteria was present in 87% of cases (hyperpigmented follicular opening, annular-granular pattern, pigmented rhomboidal structures, obliterated hair follicles). Three original criteria were also present at a relatively high frequency: increased density of the vascular network (58%), red rhomboidal structures (40%), target-like patterns (41%). Darkening at dermoscopic examination (when compared with naked-eye examination) was observed in 25% of lesions. Classical dermoscopic features of extrafacial melanoma (atypical pigment network, irregularly distributed globules, dots, streaks and pseudopods) and vertical growth phase-associated dermoscopic criteria (ulceration, blue papular areas and black structureless areas) were rarely seen. A large number of colours, pigmented rhomboidal structures, obliterated hair follicles and red rhomboidal structures were significantly more frequent in invasive LMMs. In contrast, in situ melanomas were more often associated with one or two colours and few distinctive dermoscopic features.

Conclusions: We present herein, in a large series of LMM, confirmation of the diagnostic value of the classical Stolz dermoscopic criteria and describe four additional original criteria, mainly vascular. A correlation between the presence of some dermoscopic features and thicker tumoral invasion has also been demonstrated.