Fibrous Histiocytoma

The deep margin of fibrous histiocytomas usually shows limited infiltration into the subcutaneous tissues. This is in contrast to the more extensive infiltration seen in dermatofibrosarcoma protuberans (DFSP). DFSP has a more homogenous population of tumor cells and lacks inflammatory cells, foamy histiocytes, and giant cells. Storiform pattern is more pronounced in DFSP and mitotic activity is increased.