Perineural inflammation in morphea (localized scleroderma): systematic characterization of a poorly recognized but potentially useful histopathological feature

The association between morphea and perineural inflammation has been reported sporadically but never studied systematically. To assess the prevalence and nature of perineural inflammation in various clinicopathologic stages of morphea and a cohort of other inflammatory dermatoses, 80 morphea and 36 control skin biopsies were studied using hematoxylin/eosin and S100 stains. Perineural inflammation was semiquantitatively analyzed (scored), which along with the pattern (concentric vs. marginal) and cellular composition was compared in the two groups. Perineural inflammation was identified in 84% and 61% of morphea and control cases, respectively. Examination of only routinely stained sections could still detect this feature in 58% of morphea and 33% of control biopsies. Mean perineural inflammation score in morphea (0.65) was significantly higher than in the control group (0.23) (p < 0.0001) and the inflammation tended to show a concentric pattern with plasma cell neurotropism. Intraneural inflammation was limited to four morphea cases. Although perineural inflammation is common in morphea, it is not unusual to find this feature in other inflammatory conditions. Nevertheless, perineural inflammation can serve as an important diagnostic adjunct in difficult cases of morphea if one considers its greater intensity, predominantly concentric pattern and the tendency to show plasma cell neurotropism.