Reactive neuroepithelial aggregates of the skin.

A peculiar, apparently reactive, microscopic structure of the skin was observed in 5 patients. It is characterized histologically by a bundle of nerve fibers partially or completely ensheathed by bland nonkeratinizing squamous epithelium. In 2 patients, the specimens were reexcision specimens, in which this structure was found amid active postbiopsy repair. In the remaining 3 patients, there was no history of previous excision or trauma at the lesional sites, and the background changes were consistent with either folliculitis or prurigo nodularis. This structure, when viewed in isolation, resembles carcinomatous perineural invasion. This structure and comparable structures observed in extracutaneous sites have often been referred to as "perineural invasion" in the literature, but the author proposes the term reactive neuroepithelial aggregate (RNEA) to denote its reactive nature.