Plasmacytoid dendritic cells in granulomatous variant of mycosis fungoides

Abstract

Introduction Granulomatous mycosis fungoides (MF) is a rare variant in which granulomas are associated with other typical signs of MF. Its prognosis is worse than that of classical MF. Plasmacytoid dendritic cells (PDCs) are a subset of interferon‐producing dendritic cells that link the innate and the adaptative immune responses. They have also been related to tolerance to certain tumors such as melanoma. Materials and methods In this article, we examined for the presence of CD123+ PDC in six cases of granulomatous MF from our archives. Results We found clusters of 10 or more positive cells in three of six cases of granulomatous MF (two women and a man, in their sixth and seventh decade). Although in two of these three cases the granulomatous response was extensive, in the other, it only represented 10% of the infiltrate of the biopsy. In all three cases, the granulomas were epithelioid, sarcoidal type. Conclusions CD123+ PDC can be identified in granulomatous MF. The pathogenic and prognostic role of this finding requires further clarification.

CD123 immunoexpression in cutaneous lupus erythematosus, polymorphous light eruption, pityriasis rosea, and mycosis fungoides

“…Previous two studies of Pileri et al showed that PDC was rare in MF patients, but when the stages were compared, it is significantly higher in stage IIB than stage IA/B disease [37]. The cluster of CD123+ PDC was detected in 3 of 6 patients with granulomatous MF and it implies CD123 immunoreactivity could be identified in granulomatous MF [24]. Additionally, recent studies showed that CD123+ PDCs tend to contribute to cuta- neous granulomatous disorders such as granuloma annulare, granulomatous foreign body reactions, and even cutaneous sarcoidosis [38][39][40].…”

“…Type 1 interferon produced by PDCs has a critical role in the onset, progression, and activation of autoimmune and immuno-allergic dermatoses, cutaneous neoplasms, and infectious diseases [13,19,22,23]. Surface expression of interleukin-3 receptor α chain (CD123), which is easily demonstrated by immuno- histochemical stains, is used in the differential diagnosis of LE cases to distinguish them from inflammatory/ autoimmune diseases [24][25][26][27]. The number and distribution of PDCs also differ markedly in inflammatory and neoplastic diseases.…”