Objective　The nature of myoid/myofibroblastic differentiation in dermatofibrosarcoma protuberans (DFSP) and its clinical and pathological significance were studied. Methods　124 DFSPs were reviewed by light microscopy. 6 cases with areas of myoid/myofibroblastic differentiation were assayed with immunohisto-chemical technique and electron microscopy was applied in two cases. Results　Myoid/myofibroblastic differentiation occurred most commonly in fibrosarcomatous DFSP (FS-DFSP). It was recognized histologically as peripherally distributed or randomly scattered small eosinophilic nodules or short bundles, which were composed of bland spindle cells, closely resembling smooth muscle cells or myofibroblasts. Immunohistochemically, cells in myoid/myofibroblastic areas showed positive staining for α-SMA, MSA and vimentin, but negative for desmin and CD34. Electron microscopic study displayed the presence of microfilament bundles, focal dense bodies and micropinocytic vesicles, consistent with those of myofibroblasts. Conclusion　Myoid/myofibroblastic areas in DFSP possibly represents the hyperplasia of stromal myofibroblasts, rather than true myofibroblastic differentiation of the neoplastic cells.