ABSTRACT
A small number of melanocytic nevi develop before birth. Such nevi are generally larger than acquired nevi. They more often extend into the lower reticular dermis, exhibit more complex histological phenotypes, for example, extensive neurotization or blue-nevus-like areas, and manifest a somewhat greater propensity to malignant change that can assume unusual forms. Nonetheless, the similarities between congenital and acquired nevi are legion, and many of the special characteristics of congenital nevi relate directly to their greater size and more extensive involvement of the skin. Indeed, in case of a congenital nevus that is in the size range of acquired nevi, there is no parameter other than documented presence at birth which reliably sets it apart from acquired nevi.
