Plasmacytoid dendritic cells in hypertrophic discoid lupus erythematosus: an objective evaluation of their diagnostic value.

Background: Hypertrophic discoid lupus erythematosus (HDLE), a rare variant of lupus skin disease, is difficult to distinguish from squamous neoplasms and certain dermatoses microscopically. Recently, recognition of the pathogenetic significance of plasmacytoid dendritic cells (PDCS) in cutaneous lupus erythematosus (LE) and of their patterns of distribution in different manifestations of the disease prompted us to study their diagnostic value in the context of HDLE.
Methods: Using immunohistochemistry (CD123) to label the cells, we examined their quantities and patterns of distribution in 27 tissue samples of HDLE from nine patients compared with 39 inflammatory and neoplastic control samples from 36 patients.
Results: Using three parameters pertaining to PDCs: (i) their representation of 10% or more of the inflammatory infiltrate, (ii) their arrangement in clusters of 10 cells or more and (iii) their presence at the dermoepidermal junction, we found them to have significant diagnostic value, with accuracies of 77%, 74% and 71%, respectively.
Conclusions: This study supports the careful descriptive observations of previous authors in the field. It also lends validity to the diagnostic step of mapping, immunohistochemically, the density and distribution of PDCs in suspected cases of HDLE.
(© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)