Dermatofibrosarcoma protuberans (DFSP) is a rare, malignant soft tissue tumor. It arises from the dermis, however, a few lesions are known to infiltrate into deeper layers. It commonly occurs on the trunk and extremities, but rarely involves the breast. We report a case of a 43-year-old woman who had histologically proven DFSP of the breast, with emphasis on ultrasonographic findings and pathological features. In our case, the ultrasonographic features of DFSP revealed an ovalshaped hypoechoic mass in the dermis of left breast with surrounded by increased levels of echogenic subcutaneous fat. This ultrasonographic finding correlated with pathologic features of infiltration of tumor cells into the subcutaneous fat. No previous study reported this feature of DFSP associated with the breast.
