Neurofibromatous changes in dermatofibrosarcoma protuberans: a potential pitfall in the diagnosis of a serious cutaneous soft tissue neoplasm.
Dermatofibrosarcoma protuberans (DFSP) is a low-grade malignant neoplasm that has the potential for aggressive local growth and destruction if not treated appropriately. Although the storiform arrangement of spindle cells in DFSP is relatively characteristic, histologic patterns simulating other benign as well as malignant neoplasms such as dermatofibroma, neurofibroma, malignant fibrous histiocytoma, and atypical fibroxanthoma have been described. We collected and analyzed six cases of probable DFSP in which a specific diagnosis could not be rendered due to the predominant neurofibromatous changes in the histologic sections. In an attempt to reach a definitive diagnosis, the clinical history and physical characteristics of the lesions were taken into account, and all cases were further evaluated using immunostaining for CD34 and S-100 protein. The average age of the patient was 56 years (range 21-80), and the male to female ratio was 1 : 1. The location of lesions included the scalp, neck, back, and abdomen. All cases displayed two distinct histological patterns: (i) a proliferation of spindle cells with wavy nuclei in a loose mucinous stroma suggesting neural differentiation and (ii) a proliferation of spindle cells which interweaved and filled the reticular dermis extending into the subcutis. The wide variety of clinical impressions and descriptions indicated that the diagnoses were not always straightforward, and clinical information did not always assist in the clinicopathologic correlation. All lesions stained positively for CD34; however, three of six cases also stained positively for S-100. The three cases which were CD34 positive and S-100 negative were likely DFSP, and this was the final diagnosis given. The three cases that were CD34 and S-100 positive did not allow for a straightforward diagnosis. DFSP may demonstrate areas with features more characteristic of a benign neural lesion, such as a neurofibroma, which can lead to underdiagnosis and subsequent failure to treat. Clinicians and pathologists should recognize this potential diagnostic pitfall and understand that equivocal clinical information, combined with non-specific immunohistochemical staining patterns, can further complicate the dilemma. In these situations, where DFSP is the likely diagnosis but definitive evidence cannot be obtained, full excision of the lesion should be recommended to avoid mistreatment of a potentially malignant lesion.