Desmoplastic fibroma of bone. An ultrastructural study.

The ultrastructure of three cases of desmoplastic fibroma of bone is presented. The lesion is principally characterized by myofibroblasts admixed with lesser numbers of fibroblasts and primitive mesenchymal cells. Thus, the cellular composition is similar to that described in a variety of nonneoplastic proliferative processes of soft tissue. It is postulated that the myofibroblastic proliferation develops in response to unknown factors acting on marrow fibroblasts or primitive mesenchymal cells.