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RESEARCH PRODUCT

Immunoreactivity using anti-ERG monoclonal antibodies in sarcomas is influenced by clone selection.

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The aim of the present study was to explore ERG immunoreactivity in a series of sarcomas, GIST and malignant rhabdoid tumor (MRT), considering the not fully elucidated specificity and sensitivity of this antibody. Paraffin-embedded tissue microarrays from those tumors were stained with anti-ERG against the C-terminus [(EPR3864(2)] and N-terminus (Clone 9FY). EPR3864(2) was positive in almost all angiosarcomas, and MRT.GIST were positive in a large proportion of cases (38.4%), and more than half the synovial sarcomas (52.7%) revealed EPR3864(2) staining. Several chondrosarcomas, osteosarcomas, rhabdomyosarcoma and Ewing's sarcoma family of tumors (ESFT) presented EPR3864(2) expression in a lower number of cases. 9FY was positive in most of the angiosarcomas; however, only sporadic ESFT and synovial sarcoma were positive and the other tumors tested were negative. Fourteen ESFT with EWSR1/Fli-1 gene fusion presented positive nuclear staining for EPR3864(2). Similarly, 5 ESFT with EWSR1/Fli-1 gene fusion presented positive staining for 9FY. We must stress that the difference between the present and previous studies may be due to the source of the anti-ERG employed, anti-ERG against C or N-terminus, protein cross-reactivity and dilution. In conclusion, specificity for ERG staining in sarcomas should be considered with caution and the immunoexpression is undoubtedly influenced by clone and antibody selection. (C) 2014 Elsevier GmbH. All rights reserved.