Dermatofibrosarcoma protuberans is a unique fibrohistiocytic tumour expressing CD34.

Dermatofibrosarcoma protuberans (DFSP) is a slow growing, locally invasive tumour whose differentiation from other fibrohistiocytic tumours sometimes poses serious diagnostic problems. We investigated CD34 expression immunohistologically in various fibrohistiocytic tumours including dermatofibroma, DFSP, malignant fibrous histiocytoma (MFH), infantile myofibromatosis, fibrosarcoma, hypertrophic scar and keloid. Among these, DFSP was unique in that tumour cells themselves expressed CD34, whereas in other tumours. CD34 expression was observed only on vascular endothelial cells amongst the tumour cells. Until now, there have been no reports of useful immunohistological markers for DFSP. CD34 expression by the tumour cells can be an extremely useful marker in establishing a definitive diagnosis of DFSP.