Schechter SA, et al. - In the present study, the researchers sought to assess the significance of fat necrosis associated with lymphocytic infiltrate as a histopathologic clue to distinguishing cellular dermatofibromas (CDFs) from dermatofibrosarcoma protuberans (DFSP). Cases have been identified in the pathology database with a primary CDF or DFSP diagnosis. Punch or excisional biopsy specimens with extension into the subcutis have been selected. Previously biopsied lesions and specimens that did not interact with the subcutis have been removed. In 20/20 cases of CDF, fat necrosis with lymphocytic infiltrate was present. None of the 20 cases of DFSP had fat necrosis with lymphocytic infiltrate, although 4/20 had fat necrosis alone. Fat necrosis with associated lymphocytic response may help to distinguish between CDF and DFSP.