Dermatofibrosarcoma protuberans with fibrosarcomatous areas. A clinicopathologic study of nine cases and a comparison with allied tumors.

Nine cases of dermatofibrosarcoma protuberans with fibrosarcomatous areas (DFSP with FS) were analyzed clinicopathologically, and the findings compared with allied tumors comprising 43 cases of ordinary DFSP, ten of superficial fibrosarcoma (SFS), and 11 of storiform variant of malignant fibrous histiocytoma (SV MFH). All but one case of DFSP with FS developed on the trunk of the body. Eight of the nine patients (89%) had one recurrence with a shorter prerecurrent interval than that of the ordinary DFSP, and a hipbone metastasis was identified in one patient. These findings reflect the unfavorable course, in contrast to the ordinary DFSP. Microscopically, the FS areas were presented either in the initial lesion (five cases) or in the recurrent one (four cases), areas showing cellularity, mitotic figures, and cytologic anaplasia that exceeded those in the DFSP areas. Dermatofibrosarcoma protuberans with FS and allied categories such as SFS and SV MFH shared various clinical and histologic features but there was a diversity in the prognosis relative to the grade of malignancy. The relationship between DFSP with FS and the allied tumors was given attention.