Lichen planopilaris: histopathological survey of 70 vertical sections of scalp biopsies

Lichen planopilaris (LPP) is the most common form of immune-mediated scarring alopecia. We evaluated the histopathologic features of LPP in vertical sections of scalp biopsies and compared findings between the scarring and nonscarring phases of the disease. From June 2019 to June 2020, vertically sectioned scalp biopsies of 70 new cases of LPP were examined (H&E) according to North American Hair Research Society criteria. Furthermore, patients were divided into two groups based on either the presence or the absence of vertical fibrous bands, and other histopathological features were compared between these two groups. Characteristic findings of LPP were perifollicular lymphocytic infiltration (97.1%), follicular interface degeneration (60%), and perifollicular plasmacytic infiltration (21.4%). Vacuolar degeneration in the dermo-epidermal junction (38.6%), perifollicular lamellar fibroplasia (67.1%), loss of sebaceous glands (87.1%), perifollicular cleft formation (28.6%), and vertical fibrous tracts (65.7%) were also found. Furthermore, we found a significant correlation between the presence of fibrous tracts with both loss of sebaceous glands (P = 0.005) and the presence of lamellar fibroplasia (P = 0.015). The most common findings in the histopathological examination of LPP slides are perifollicular lymphocytic infiltration and loss of the sebaceous glands. Furthermore, sebaceous gland loss and perifollicular lamellar fibroplasia correlate with the scarring phase of LPP.