DERMATOFIBROSARCOMA PROTUBERANS AND ITS FIBROSARCOMATOUS VARIANT WITHAREAS OF MYOID DIFFERENTIATION - A REPORT OF 3 CASES

Aims: We describe three examples of dermatofibrosarcoma protuberans wh ich demonstrated focal myofibroblastic differentiation, and discuss th e nature of myofibroblastic differentiation. Methods and results: Mie studied three cases of dermatofibrosarcoma protuberans, two of which h ad fibrosarcomatous portions containing myoid areas, and one which sho wed myoid areas in ordinary dermatofibrosarcoma protuberans, Myoid are as were recognized histologically as randomly distributed, scattered b undles or small nodules of spindle cells with deeply eosinophilic cyto plasm, Myofibroblastic differentiation was demonstrated immunohistoche mically by positive staining for smooth muscle actin and muscle-specif ic actin, and ultrastructurally by the presence of microfilament bundl es with focal dense bodies and pinocytic vesicles. The myoid areas occ asionally contained intraneoplastic blood vessels. Conclusion: The pre sence of myoid areas may be related to reactive hyperplasia of stroma, and its relation to the histogenesis of dermatofibrosarcoma protubera ns is uncertain.