Dermatoscopy of melanoma according to type, anatomic site and stage: a 2020 update

The indisputable contribution of dermatoscopy in early diagnosis of melanoma is widely recognized. In the last quinquennium, new data concerning specific melanoma subtypes have come to light. The dermatoscopic morphology of superficial spreading melanoma (SSM) has been extensively investigated in the literature. Atypical network, irregular dots, irregular globules, irregular streaks and irregular blotch correspond to histopathologic alterations at the level of the junction, blue-white veil and atypical vessels suggest intradermal growth, whereas regression structures, negative network and white shiny streaks might reflect junctional or dermal alterations. The list of melanoma specific criteria has been recently updated to include features that typify early melanoma, such as irregular hyperpigmented areas and prominent skin markings and features seen in melanoma on sun damaged skin such as angulated lines. Nodular melanoma lacks most of the aforementioned criteria and is typified by the coexistence of blue and black color, atypical vessels and pink color. Lentigo maligna dermatoscopic criteria mainly develop at the outline of the follicular openings. However, at an early stage these features might be very subtle and the diagnosis should be based on the exclusion of benign tumors (inverse approach). Acral lentiginous melanoma is typified by a parallel ridge pattern, but also SSM criteria should be taken into consideration. The diagnosis of subungual melanoma is based on the assessment of the color and characteristics of the pigmented nail band. For the diagnosis of mucosal melanoma, the assessment of colors is more informative than the assessment of structures and the detection of blue, white or gray should raise the suspicion of melanoma. White shiny streaks and regression structures are the most common features of desmoplastic melanoma. The diagnosis of nevoid melanoma might be highly challenging and require information on the lesion's history. Melanoma on small- and medium-sized congenital nevi is typified by an eccentric location of the suspicious area, negative network and gray angulated lines. Recent advances in knowledge on the dermatoscopic characteristics of peculiar subtypes of the tumor significantly enrich the diagnostic armamentarium of clinicians. The challenge of the forthcoming years is to better characterize biologically aggressive melanomas and to optimize the screening strategies so as to identify them.