FIBROSARCOMATOUS DERMATOFIBROSARCOMA PROTUBERANS - A VARIANT

We report two examples of dermatofibrosarcoma protuberans with fibrosa rcomatous change, in which the fibrosarcomatous component of the tumor demonstrated focal myofibroblastic differentiation, This was recogniz ed by light microscopy as plump myoid cells associated with abundant e xtracellular collagen production, immunohistochemically by positive st aining for smooth muscle and muscle specific actin, and ultrastructura lly by subplasmalemmal filament aggregates and micropinocytotic vesicl es, Myofibroblastic differentiation has not been described before in d ermatofibrosarcoma protuberans with fibrosarcomatous change and becaus e of a lack of information concerning the immunohistochemical profile of this variant of DFSP its incidence is unknown. Focal myofibroblasti c differentiation, as demonstrated in the fibrosarcomatous regions of these two tumors, might support the proposed dermal fibroblastic origi n for dermatofibrosarcoma protuberans with fibrosarcomatous change.