Langerin is used for the visualization of normal and neoplastic Langerhans cells. These cells reside in the skin, usually as scattered cells along the dermal-epidermal junction. Langerin is expressed in both normal and neoplastic Langerhans cells and is specifically associated with the assembly of Birbeck granules in these cells. Immunohistochemical evaluation of Langerin expression is used to confirm a diagnosis of Langerhans cell histiocytosis and differentiating it from non-Langerhans cell histiocytic proliferations.