Indeterminate cell histiocytosis

A rare neoplastic disease characterized by multiple, and on occasion single, asymptomatic, smooth, red-brown papulonodules located on the face, neck, trunk and/or extremities which present a nonepidermotrophic histiocytic infiltrate with immunohistochemical features of both Langerhans and non-Langerhans cells (i.e. immunopositive for S100 protein and CD1a in the absence of Birbeck granules and langerin expression).