Dermatofibrosarcoma protuberans arizing in the thigh of a 23-year-old female is reported with an investigation of tumor cell character by electron microscopy, enzyme histochemistry, immunological and in vitro tissue culture techniques. The tumor tissue showed histologically a peculiar storiform arrangement of plump spindle cells with dense proliferation. Electron microscope revealed histiocytic cell structures of some tumor cells: lysosomes, phagosomes, and sparse rough endoplasmic reticula. They revealed diffuse positive reactions to acid phosphatase (Ac Pase) and non-specific esterase. Short-time culture of the tumor tissue indicated rather round and polygonal cells admixed with spindle cells, positive to Ac Pase and non-specific esterase with diffuse reaction. Most of the round cells possessed Fc and C3 receptors on their surface and phagocytic activity. Dermatofibrosarcoma protuberans is probably a histiocytic tumor and structural characteristics of schwann cells were not recognized.