Sclerosing dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans is a low-grade sarcoma of the skin with well characterized clinical and histopathological features. The lesion frequently appears as a plaque on the trunk or on the extremities of middle-aged adults. Microscopically, the tumor is composed of monomorphous spindle cells arranged in storiform pattern and embedded in a sparse to moderately dense fibrous stroma. We report on two unusual cases of dermatofibrosarcoma protuberans in which neoplastic cells were diffusely replaced by sclerotic tissue in more than 50% of the entire tumor. In both cases, no external trauma or radiotherapy were recorded. Since tumor regression has been defined as a loss of tumor mass in the absence of any treatment (or trauma) we believe that sclerosis in DFSP may represent a manifestation of regression and not, as previously suggested, a new variant of the neoplasm.