title: HER2 Gene Protein Assay Is Useful to Determine HER2 Status and Evaluate HER2 Heterogeneity in HER2 Equivocal Breast Cancer.
abstract: OBJECTIVE
  Approximately 15% of breast cancers show equivocal human epidermal growth factor receptor 2 (HER2) results on HER2 immunohistochemistry (IHC) and are reflexed for fluorescence in situ hybridization (FISH). However, some cases remain equivocal. In this study, we evaluated these double-equivocal cases by using a novel gene protein assay (GPA), which can simultaneously assess HER2 gene copy number and protein on a single slide using bright-field microscopy.
  
  
  METHODS
  GPA was performed on 42 HER2 IHC and FISH double-equivocal cases.
  
  
  RESULTS
  GPA was negative for amplification in 28 cases, equivocal in three cases, and positive in 11 cases. The GPA results showed excellent concordance with either repeat FISH using a chromosome 17 centromere probe or FISH using an alternative probe. Furthermore, HER2 heterogeneity was identified in three of 11 GPA-positive cases.
  
  
  CONCLUSIONS
  HER2 GPA performs accurately and is very useful to determine HER2 status in HER2 IHC and FISH double-equivocal breast cancer cases and identify HER2 heterogeneity.
authors.affiliation: From the Department of Pathology, Wexner Medical Center at The Ohio State University, Columbus.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Ventana Medical Systems, Tucson, AZ.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nitta
authors.affiliation: From the Department of Pathology, Wexner Medical Center at The Ohio State University, Columbus.
authors.forename: Zaibo
authors.initials: Z
authors.lastname: Li
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D018734:Genes, erbB-2 / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D017403:In Situ Hybridization / Q000379:methods*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: Breast carcinoma; Fluorescence in situ hybridization; HER2 gene protein assay; HER2 heterogeneity; Immunohistochemistry