OBJECTIVE Dermatofibrosarcoma protuberans is a distinct clinicopathologic entity characterized by fibroblasts with a prominent storiform pattern. It accounts for about 6% of all soft-tissue sarcomas. The lesion is typically superficial, and the diagnosis can be suspected on the basis of the tumor's clinical appearance. Consequently, the imaging appearance of this entity is essentially unreported. Large lesions, however, can infiltrate the deep soft tissue and be confused with higher-grade sarcomas. We report the radiologic appearance in 11 cases of histologically proved dermatofibrosarcoma protuberans. METHODS The radiologic images of 11 patients who had histologically verified dermatofibrosarcoma protuberans were retrospectively studied. The patients included eight males and three females 9-47 years old (mean, 33 years). Each had a soft-tissue mass that had been present for a variable period, from 3 months to 23 years. CT scans were available for review in six cases, MR images in four, radiographs in nine, bone scintigrams in three, and arteriograms in three. RESULTS All lesions were unmineralized nodular masses involving the skin and subcutaneous adipose tissue. The size, in greatest dimension on imaging studies, was 3-22 cm. CT scans (six cases) showed a well-defined lesion with a distinct lobular or nodular architecture and tissue attenuation approximately equal to or greater than that of skeletal muscle. Moderate enhancement was seen on CT scans obtained after injection of contrast material. Arteriograms (three cases) showed mild to moderate hypervascularity. The MR appearance (four cases) was nonspecific; the lesions had prolonged T1 and T2 relaxation times. In one case, MR images showed multiple nodular lesions. Radiographs (nine cases) showed a soft-tissue mass or soft-tissue swelling without evidence of bone involvement or calcification. Bone scintigrams (three cases) showed increased accumulation of tracer. CONCLUSIONS The radiologic appearance of dermatofibrosarcoma protuberans is typically that of an unmineralized, nodular soft-tissue mass involving the skin and subcutaneous adipose tissue. CT scans or MR images are well suited to show this location, the relation of the lesion to underlying structures, and the distinct lobular or nodular architecture. Arteriograms will show mild to moderate hypervascularity and bone scintigrams will show increased accumulation of radiopharmaceutical.