Summary: Langerhans 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.
1Department of Pediatric Pathology, University of Ottawa
2Department of Pediatric Pathology, Children's Hospital of Eastern Ontario
3Department of Innovations in Medical Education, University of Ottawa
4Departments of Pediatric Surgery, University of Ottawa, and Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
Address for correspondence: A/Prof Dina El Demellawy, University of Ottawa, Department of Pediatric Pathology, Children's Hospital of Eastern Ontario (CHEO), 401 Smyth Road, Ottawa, ON K1H 8L1, Canada. E-mail firstname.lastname@example.org
Received 24 September, 2014
Revised 24 December, 2014
Accepted 11 January, 2015