 There is an association with sunburn, but causation is not established.Genetic studies of Spitz nevi have shown that most cells have the normal number of chromosomes, however a minority (25%) of cells have been shown to contain extra copies of parts of some chromosomes, such as the short arm of chromosome 11 (11p).On histopathology, Spitz nevi characteristically have vertically arranged nests of nevus cells that have both a spindled and an epithelioid morphology.