Clark's nevus

"Clark's nevi" is the name we apply to lesions that have been referred to i n the past as dysplastic nevi or nevi with architectural and/or cytologic a typia, Our criteria for this histopathologic diagnosis include such archite ctural features as: (1) uneven distribution of melanocytes along the dermoe pidermal junction; (2) irregularly spaced junctional nests that sometimes b ridge between rete; and (3) ill-defined margins often characterized by a le ntiginous growth pattern. If dermal nests are present, the junctional compo nent usually extends laterally for some distance beyond the dermal nests. W hen there is cytologic atypia, it involves scattered melanocytes. Clark's n evi are of doubtful significance if few in number and occurring in a young patient in whom there is no family history of melanoma. When many are found in a patient with a family history of melanoma, their presence serves as a marker for dysplastic nevus syndrome (familial atypical mole-melanoma synd rome). When Clark's nevi develop in patients older than 40 or 50 years of a ge who have no family history of melanoma, their significance is less clear , However, they might signify a defect in those mechanisms that normally co ntrol formation and growth of melanocytic neoplasms. Copyright (C) 1999 by W.B. Saunders Company.