Histology: Dermatofibrosarcoma protuberans shows an infiltrative growth pattern. It invades the subcutaneous fat tissue. The tumor cells can be seen encasing adipocytes. The tumor is poorly circumscribed, and its borders can be difficult to distinguish from normal dermis. The tumor itself is made up fibroblasts arranged in a storiform pattern. These tumors stain positively with the CD34 immunohistochemical stain and are negative for factor XIII. These two stains are often used to differentiate dermatofibrosarcoma protuberans from the benign dermatofibroma, which has the opposite staining pattern. The stromolysein-3 stain is also used to help differentiate the two tumors; it is positive in cases of dermatofibroma and negative in cases of dermatofibrosarcoma protuberans.
Treatment: Because of the ill-defined nature of the tumors and their often large size at diagnosis, wide local excision with 2- to 3-cm margins is often undertaken. Postoperative localized radiotherapy has been used to help decrease the recurrence rate. Imatinib has shown promise in dermatofibrosarcoma protuberans as a treatment before surgery to help shrink large or inoperable tumors. There has also been anecdotal success with the use of imatinib in metastatic disease.
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