The rôle of the reticulo-endothelial cell in many medical disorders has received increasing attention in recent years, and perhaps in no field has it modified the conception of various diseases more than in dermatology. It is thought by many observers that the evolution of this cell is responsible for the development of the granulomas of mycosis fungoides, Hodgkin's disease and the cutaneous leukemias, and it is generally conceded now that the xanthoma cell is a histiocyte modified by the storing of cholesterol esters.1 We have stated elsewhere2 that the tumors of nevoxantho-endothelioma, first described by McDonagh, consist of modified histiocytes and that these lesions represent merely a form of juvenile xanthoma. Recently we became interested in the rôle of the histiocyte in the production of a common and generally recognized tumor which has received relatively little attention in the literature. This is the lesion described by