Papular epidermal nevus with "skyline" basal cell layer (PENS) following a Blaschko linear pattern.

Papular epidermal nevus with "skyline" basal cell layer (PENS), a variant of epidermal nevi, has recently been described as a small, round or polygonal papule, visible at birth or shortly thereafter, with characteristic histopathologic features. It has been considered a separate entity from keratinocytic nevi because no lesion observed thus far has followed any of the known archetypical mosaic patterns. Here we describe for the first time a PENS lesion following a linear distribution pattern along Blaschko's lines.