In vitro examination of cell proliferation in dermatofibroma and in the overlying epidermis.

In nine typical cases of dermatofibroma autoradiographic methods were used to examine the proliferative activity in the tumor and in the overlying epidermis. The number of DNA-synthesizing cells in the dermal nodular lesions was extremely low (0 -- 0.1%). In seven of nine skin lesions acanthosis was to be seen in the overlying epidermis. The quantity of DNA-synthesizing cells in the epidermis overlying the dermatofibroma was not related to the thickness of the epidermis and remained independent, whether the predominant element in the tumor is fibrillar or cellular. In this study we were able to demonstrate the existence of a direct relation between the degree of epidermal proliferation and the distance between the tumor and the epidermis. The duration of DNA-synthesis was constant.