Value of CD123 Immunohistochemistry and Elastic Staining in Differentiating Discoid Lupus Erythematosus from Lichen Planopilaris

BACKGROUND: Differentiating scarring alopecia secondary to lichen planopilaris (LPP) and discoid lupus erythematosus (DLE) has always been a challenge clinically and pathologically. Plasmacytoid dendritic cells (PDCs) have been reported in the cutaneous lupus erythematosus by CD123 immunostaining. This study assesses CD123 marker positivity and patterns of elastic fiber loss in scalp biopsy to differentiate DLE from LLP. PATIENTS AND METHODS: Forty-three cases with clinical and pathological diagnosis of LPP and DLE were selected, and CD123 immunohistochemistry staining and elastic staining were performed on them. The presence of CD123-positive cells, clustering and distribution of cells, and patterns of elastic fibers loss in the dermis were evaluated. To analyze the data, the Chi-square test was used; moreover, the sensitivity and specificity of CD123 were calculated based on a diagnostic test for 2-by-2 tables. RESULTS: Infiltration of PDC was seen in 90% of DLE cases. The presence of more than 10% and 20% PDC cells in inflammatory cells had 90% and 85% sensitivity and 34.7% and 91.3% specificity, respectively. PDC clusters more than 20 cells had 100% specificity for DLE. Location and patterns of PDC infiltration were not statistically significant (P = 0.378). The wedge-shaped loss of elastic fibers and the diffuse loss were the dominant patterns in LPP and DLE, respectively (P = 0.006). CONCLUSION: Our results suggested that CD123 along with elastic staining and histological features might be useful to diagnose challenging cases of lymphocytic scarring alopecia with clinical differential diagnosis of LPP and DLE.