EXPRESSION OF THE HUMAN PROGENITOR-CELL ANTIGEN CD34 (HPCA-1) DISTINGUISHES DERMATOFIBROSARCOMA PROTUBERANS FROM FIBROUS HISTIOCYTOMA IN FORMALIN-FIXED, PARAFFIN-EMBEDDED TISSUE

Background: Histologic distinction of dermatofibrosarcoma protuberans (DFSP) from fibrous histiocytoma (FH) may be difficult. In addition, differential diagnosis is hampered by the lack of appropriate immunohistochemical markers that reliably distinguish between these two entities. Objective: This study is aimed at the introduction of a monoclonal antibody (anti-human progenitor cell antigen-1; anti-CD34) that distinguishes between DFSP and FH in formalin-fixed, paraffin-embedded tissue. Methods: Paraffin-embedded specimens of DFSP, FH, and other soft-tissue tumors were investigated for CD34 expression by anti-human progenitor cell antigen-1/alkaline phosphatase-antialkaline phosphatase immunostaining. Results. Strong CD34 reactivity was present in each DFSP (n = 19) but was consistently absent from FH (n = 45) and other soft-tissue tumors (n = 47). Conclusion: CD34 immunostaining of paraffin-embedded specimens may be useful in differentiating between DFSP and FH.