Have a look at this article which I found quite interesting:
The evolution of nevi is a complex process involving several constitutional and environmental factors. Although histopathology is the gold standard for the diagnosis and classiﬁcation of melanocytic nevi, the widespread use ofin vivo diagnostic technologies such as dermoscopy and more recently of reﬂectance confocal microscopy, hasenriched profoundly our knowledge regarding the morphological variability of nevi in different stages of their evolution. In addition, signiﬁcant progress has been made in our understanding of genetic alterations and molecular pathways involved in the formation of melanocytic tumors. All this newly acquired knowledge increasingly questionswhether morphologically different nevi are also histiogenetically different. In this article, we intend to extract some ofthe salient points from published clinical and molecular studies on melanocytic tumors and attempt to assimilatethem into an integrative concept of nevogenesis.