Spitz naevi and melanomas with similar dermoscopic patterns: can confocal microscopy differentiate?

Background Differentiating Spitz naevi from melanomas can be difficult both clinically and dermoscopically. Previous studies have reported the potential role of in vivo reflectance confocal microscopy (RCM) in increasing diagnostic accuracy. Objectives To define RCM criteria that can differentiate 'false twins', namely Spitz naevi and melanomas sharing similar dermoscopic appearance. Methods Lesions histopathologically diagnosed as Spitz naevi or melanomas were retrospectively retrieved. They were selected to cover all dermoscopic types and were put into couples sharing similar aspects. Lesions were classified into three main dermoscopic categories: globular and starburst pattern, spitzoid with dotted vessels, and multicomponent or aspecific pattern. Results RCM findings revealed that striking cell pleomorphism within the epidermis, widespread atypical cells at the dermoepidermal junction and marked pleomorphism within nests were significantly associated with the diagnosis of melanoma, while spindled cells and peripheral clefting were found exclusively with and pathognomonic of Spitz naevi. Furthermore, the analysis of a dermoscopic subgroup highlights the importance of striking pleomorphism and spindled cells as clues to differentiate 'false twins' with globular or starburst patterns. Conclusions The current study highlights the role of RCM in discriminating 'false twins' of Spitz naevi and melanomas for lesions showing starburst and globular patterns on dermoscopy, whereas RCM is not useful in the other dermoscopic subgroups.