Dermatofibrosarcoma protuberans. A clinicopathologic review with emphasis on fibrosarcomatous areas

We reviewed 75 cases of dermatofibrosarcoma protuberans (DFSP) from the University of Texas M.D. Anderson Cancer Center. All accessions were examined for areas of giant cell fibroblastoma (GCF), but none was found. The 30 cases having a minimum of 5 years follow-up were studied in more detail. The histologic findings were typical of DFSP in 24 cases, whereas in six cases discrete areas with a fascicular or "herringbone" growth pattern, considered to represent fibrosarcomatous change (DFSP-FS), were evident. The mitotic rate was usually but not always higher in fibrosarcomatous areas, and occasional examples of typical DFSP demonstrated relatively numerous mitotic figures (up to 35 per 10 high-power fields). Other histologic findings of interest were the presence of melanin in two cases of DFSP and the focal presence of a distinctive type of multinucleated giant cell similar to those seen in GCF in six cases. Patients with DFSP-FS differed from those with DFSP in that they had a higher median age (56 years vs. 37 years). Tumor location was similar in both groups, with the trunk being the most common site. No significant difference in either the rate of local recurrence or the interval until recurrence between DFSP and DFSP-FS was evident; the only factor strongly related to local recurrence was adequacy of surgical margins. However, the only two patients who died of tumor, including the sole patient with distant metastasis, had DFSP-FS. We conclude that DFSP-FS deserves recognition as a variant of DFSP.