Sclerosing nevus with pseudomelanomatous features: dermoscopic and confocal aspects

Background: Sclerosing nevus with pseudomelanomatous features (SNPFs) is a clinical and pathologic entity that mimics melanoma both clinically and histologically. The lesion is a melanocytic nevus, histologically characterized by fibrosis and a pseudomelanomatous proliferation. It is typically seen in young to middle-aged individuals, mainly on the back, where microtrauma or inflammatory changes are more frequent. Dermoscopic description of SNPF has been reported so far in one case series. Objective: The aim of our study was to describe the dermoscopic and confocal features of SNPF. Methods: Histopathologically confirmed cases of SNPF were retrospectively collected from three referral centres in Italy. Only lesions with available clinical, dermoscopic and histopathological data were included; confocal images were also retrieved, when available. Lesions were evaluated for the presence of 12 dermoscopic and five confocal criteria previously described. Results: The study population included 93 lesions in as many patients (71 men and 22 women; median age: 38 years). Dermoscopically, we found a predominance of dark colours, in particular brown and blue, which were found in all lesions and the vast majority of the lesions (86/93; 92.5%) displayed at least one structureless area. By the combination of colours and structures, we observed that the majority of the lesions (67/92; 72%) were characterized by more than one structure and more than one colour. Confocal evaluation was performed on a subset of 24/93 lesions showing a regular architecture pattern (19/24 cases, 79%), with a predominance of the ringed pattern. The presence of focal cytologic atypia at the dermal-epidermal junction was present in 12/24 cases (50%) with a prevalent dendritic-shaped cell proliferation. Conclusions: The current study demonstrated that SNPF was frequently characterized, on dermoscopic examination, by more than one structure and more than one colour and on confocal microscopy by a regular ringed pattern with focal dendritic atypical cells.