“Mistletoe sign”: probably a new dermoscopic descriptor for melanoma in situ and melanocytic junctional nevus in the inflammatory stage

Melanomas in situ (MIS) are difficult to diagnose as they lack well-established, dermoscopic descriptors. In numerous clinical cases, there are no definitive differentiating criteria between atypical nevus and melanoma in situ. So far, no digital dermoscopic criteria have been developed which can clearly distinguish atypical naevi from MIS. It is necessary to search for predictors of MIS and clinically suspected skin lesions in dermoscopy. We present 2 patients diagnosed with and treated for melanoma in situ and junctional nevus in its inflammatory stage. This includes a new morphological structure in dermoscopy known as the "mistletoe sign". Below, we have described dermoscopic pictures, with appropriate histopathology, for patients with the "mistletoe sign". Dermoscopy in two cases revealed multiple, well-circumscribed areas, consisting of non-uniform, sometimes pseudo-dichotomously branched structures, mimicking pseudopods, which were not reticular, arising from overall reticular or homogenous patterns resembling the mistletoe. Due to the fact that this is one of the several reports of its kind, further research and observation are still necessary. The "mistletoe sign" may be a descriptor of the melanocytic nevus in the inflammatory stage and the melanoma in situ; however, further studies are necessary.