“…Histological data on a total of 135 patients with PN are available in the relevant literature (Table 1). About 19 papers including case reports describe different findings, but mainly hyperkeratosis, acanthosis, papillomatosis, irregular elongation of rete ridges, or a dermal inflammatory infiltrate 9,10,13,14,16–30 . Overall, only few criteria and nondetailed descriptions were presented.…”