The fibroblastic nature of dermatofibrosarcoma protuberans. A tissue culture and ultrastructural study.

Dermatofibrosarcoma protuberans has been considered to be of fibrohistiocytic or fibroblastic origin. The purpose of this paper is to identify the original cell strain from which this neoplasm derives, using tissue culture and electron microscopic methods. Thirteen cases of DFSP characterised by clinical, topographical, histological and behavioral criteria were explanted. The emigrating cells were bipolar with two opposed processed and showed a radial arrangement in respect to the explants. After the second week the distal processes tended to curve back towards the cell body forming flame-like structures. This cell morphology and cellular orientation persisted during the whole life of the culture. Electron microscopy was performed in three cases; the newly grown cells maintained an electron microscopic picture similar to that found in the original tumors. This pattern of behaviour is characteristic of fibroblastic tumors and has been found in explants of normal fibroblasts, of fibromatosis and of fibrosarcomas used as controls. On this basis, we believe that DFSP is a fibrosarcoma of the skin of low grade malignancy.