Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH), previously known as histiocytosis X, is an abnormal clonal proliferation of Langerhans cells that is histologically characterized by papillary dermal infiltration of uniformly large ovoid cells that are 15 to 25 μm in diameter, with abundant eosinophilic cytoplasm and vesicular reniform (kidney-shaped) nuclei with inconspicuous nucleoli. Epidermotropic Langerhans cells may be prominent, both singular or in clusters.