Langerhans Cell Histiocytosis

Langerhans cell histiocytosis is a rare disease consistent in its histologic characteristics, but variable in both phenotypic presentation and prognosis. Classically, a soft tissue mass with adjacent bony destruction is often present that shows a histologic monoclonal proliferation of cells positive for CD1a, S100, and langerin (CD207). Pathognomonic Birbeck granules may be seen on transmission electron microscopy. In this review, the diagnosis, etiologies, treatments, and, most importantly, the classification schemes are discussed.