Langerhans cell histiocytosis: a comprehensive review

SummaryLangerhans cell histiocytosis (LCH) is currently regarded as a myeloid neoplasm, with remarkably broad clinical spectrum, ranging from isolated skin or bone lesions to a disseminated disease that can involve nearly any organ. LCH is generally regarded as a sporadic disease that occurs predominantly in the paediatric population. The diagnosis of LCH is confirmed by immunohistochemistry (IHC) by demonstrating the presence of dendritic cell markers such as S100 protein, in addition to CD1a and langerin. Contrary to previous beliefs, recent literature reveals that the pathogenesis of LCH might involve a clonal process implicating BRAF c.1799T>A (p.Val600Glu) and other mutations [(600DLAT) B-RAF and (T599A) B-RAF, somatic MAP2K1 mutations]. Through this review article, we have summarised the latest understanding of the biological and salient histological characteristics of LCH and its potential morphological mimics.