Dermatofibrosarcoma protuberans with fibrosarcomatous areas: a clinico-pathologic and immunohistochemic study in four cases.

Dermatofibrosarcoma protuberans (DFSP) with fibrosarcoma (FS)-like areas (DFSP-FS) is a peculiar neoplasm that combines microscopic findings of DFSP and FS. Because of the scarce number of cases published, tumor prognosis remains controversial. The clinical histories and the histologic material of 27 cases of DFSP were reviewed. Four of them showed fibrosarcomatous areas. Follow-up data, ranging from 12 to 125 months, were obtained in all four cases. Two patients had repeated local recurrences. One patient developed pulmonary metastases and died of disease 49 months after diagnosis. In the other two patients, no recurrences or metastases were detected at 12 and 70 months after local excision, respectively. Progressive increase of FS areas, cellular density, cellular atypia, and mitotic activity were observed during the recurrences. All cases showed diffuse positive immunostaining for CD34 in DFSP areas. Three cases were also CD34-positive in FS areas. Based on a careful review of the literature and our personal experience, we conclude that DFSP-FS is a rare variant of DFSP with a higher rate of local recurrences and more distant metastases than typical DFSP.