Background: The pathogenesis of acquired melanocytic nevi (AMN) is still unclear, and the origin of nevus cells has not been clarified.
Objective: To analyze the clinical features and pathological types of AMN and identify the possible origin of nevus cells.
Methods: A retrospective study of 2929 cases of AMN was conducted, and 96 specimens of intradermal and junctional nevi were selected. Immunohistochemical assays were performed to detect the expression of basement membrane component receptor DDR-1 and the molecular markers on epidermal melanocytes, dermal stem cells (DSCs), and hair follicle stem cells.
Results: Junctional nevi and compound nevi were prone to occur on glabrous skin, such as the palms, soles, and vulva, and on the extremities in children, whereas intradermal nevi tended to develop on the trunk, head, and face of adults. The immunohistochemical data revealed that both junctional nevi and intradermal nevi expressed the epidermal melanocyte surface markers E-cadherin, DDR-1, and integrin α6 and the DSC molecular markers NGFRp-75 and nestin. CD34 was expressed only in junctional nevi, whereas K19 was not expressed in any type of melanocytic nevi. There was no significant difference in molecular expression at different sites or in different ages of onset. Nestin expression was markedly stronger in the intradermal nevi than in the junctional nevi, but there was no difference between the superficial and deep nevus cell nests of intradermal nevi.
Conclusion: AMN may have a multicellular origin that commonly follows the mode of Abtropfung. Furthermore, DSCs may partly or independently participate in the formation of nevus cells.