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NCH is a type of dermal melanocytosis. Dermal melanocytosis includes a variety of pigmented lesions that are formed from the aberrant development of neural crest-derived melanocytes as they migrate to the dermis during embryogenesis [4].
In the papillary and upper reticular dermis, dendritic melanocytes are present and surrounded by fibrous sheaths (which are not present in other dermal melanocytosis, such as blue nevus or mongolian spots).
Dermal melanocytosis is thought to be due to the failure of migration of dermal melanocytes from the neural crest to the epidermal basal cell layer during fetal life, resulting in the presence of melanocytes in the dermis.1 Among different ethnic groups, over 90% of native American and people of African descent, about 80% of Asians, about 70% of Hispanics and fewer than 10% Caucasians have Mongolian spots.2 The sacral area is the classic site of involvement.