ERG and FLI1 protein expression in epithelioid sarcoma

• Published in: Modern pathology Vol. 27; no. 4; pp. 496 - 501
• Main Authors: Stockman, David L, Hornick, Jason L, Deavers, Michael T, Lev, Dina C, Lazar, Alexander J, Wang, Wei-Lien
• Format: Journal Article
• Language: English
• Published: New York Elsevier Inc 01-04-2014; Nature Publishing Group US; Elsevier Limited
• Subjects: 631/45/612/822; 692/53; 692/699/67/1798; 692/700/139; Antibodies, Monoclonal; Antibodies, Monoclonal, Murine-Derived; Antibody Specificity; Antigens, CD34 - analysis; Biomarkers, Tumor - analysis; Cancer; Cell Nucleus - chemistry; Cell Nucleus - pathology; Cross Reactions; epithelioid sarcoma; ERG; FLI1; Humans; Immunohistochemistry; Keratin; Labeling; Laboratory Medicine; Medicine; Medicine & Public Health; Monoclonal antibodies; original-article; Pathology; Platelet Endothelial Cell Adhesion Molecule-1 - analysis; Predictive Value of Tests; Protein expression; Proto-Oncogene Protein c-fli-1 - analysis; Proto-Oncogene Protein c-fli-1 - immunology; Reproducibility of Results; Sarcoma; Sarcoma - chemistry; Sarcoma - pathology; Tissue Array Analysis; Trans-Activators - analysis; Trans-Activators - immunology; Transcription factors; Transcriptional Regulator ERG; Tumors; United States > US; FLI1; epithelioid sarcoma; ERG
• ISSN: 0893-3952; 1530-0285
• DOI: 10.1038/modpathol.2013.161

Epithelioid sarcoma is a rare, aggressive keratin-positive sarcoma that co-expresses CD34 in 50% of cases and may mimic an angiosarcoma. Recently, we have observed one case of epithelioid sarcoma that labeled for ERG, an ETS family regulatory transcription factor, which is considered to be a reliable marker for vascular differentiation. We investigated the prevalence of nuclear expression of ERG and FLI1, a homologous transcription factor, in these tumors. A formalin-fixed paraffin-embedded tissue microarray of 37 epithelioid sarcomas was examined. Immunohistochemistry was performed using anti-ERG monoclonal antibody to the N-terminus, anti-ERG monoclonal antibody to the C-terminus and anti-FLI1 monoclonal antibody. Comparison was made with CD34, CD31, and D2-40 labeling. The extent of immunoreactivity was graded according to the percentage of positive tumor cell nuclei (0: no staining; 1+: <5%; 2+: 5–25%; 3+: 26–50%; 4+: 51–75%; and 5+: 76–100%), and the intensity of staining was graded as weak, moderate, or strong. Nuclear staining for the N-terminus of ERG was seen in 19 out of 28 cases: 10 with diffuse(4 to 5+) strong/moderate labeling; 1 with 2+ moderate labeling and 8 with weak labeling (1 to 4+, 2 each). Focal staining for the C-terminus of ERG was seen in only 1 out of 29 cases (2+ moderate). FLI1 labeling was seen in nearly all (28 out of 30) cases: 16 with diffuse (5+) predominantly moderate labeling, and 8 cases with diffuse(5+) weak labeling. The remainder had variable moderate (1 to 3+) or weak (1 to 4+) FLI1 staining. CD34 was positive in 22 out of 30 cases and D2-40 was found to be positive in 22 out of 31 cases. All cases were negative for CD31 (0 out of 30). Epithelioid sarcoma can label with antibodies to the N-terminus of ERG, FLI1, and D2-40, which may cause diagnostic confusion for a vascular tumor. A panel of other antibodies including SMARCB1 and CD31 should be used in evaluating these tumors. ERG antibody selection is also critical, as those directed against the C-terminus are less likely to label epithelioid sarcoma.