Hotspot analysis by confocal microscopy can help to differentiate challenging melanocytic skin lesions.

Some melanocytic lesions do not present enough clinical and dermoscopic features to allow ruling out a possible melanoma diagnosis. These "doubtful melanocytic lesions" pose a very common and challenging scenario in clinical practice and were selected at this study for reflectance confocal microscopy evaluation and subsequent surgical excision for histopathological diagnosis. The study included 110 lesions and three confocal features were statistically able to distinguish benign melanocytic lesions from melanomas: "peripheral hotspot at dermo-epidermal junction", "nucleated roundish cells at the dermo-epidermal junction" and "sheet of cells". The finding of a peripheral hotspot (atypical cells in 1mm2) at the DEJ is highlighted because has not been previously reported in the literature as a confocal feature related to melanomas.