title: Dual HER2 gene protein assay: focused study of breast cancers with 2+ immunohistochemical expression.
abstract: OBJECTIVE
  The combined gene protein assay (GPA) can simultaneously assess HER2 gene copy number and protein on a single slide using bright-field microscopy.
  
  
  METHODS
  GPA was compared with a fluorescence in situ hybridization (FISH) assay on 50 invasive breast carcinomas with a 2+ score on immunohistochemistry (IHC).
  
  
  RESULTS
  The cases were categorized into positive, equivocal, or negative for HER2 gene amplification using the 2013 American Society of Clinical Oncology/College of American Pathologists criteria. This resulted in 82% agreement (41 of 50) between FISH and GPA. In addition, 25 known IHC 3+ breast carcinomas analyzed by GPA showed protein overexpression and clusters of HER2 gene consistent with unequivocal amplification, and 22 known IHC-negative cases were negative for HER2 gene amplification by GPA.
  
  
  CONCLUSIONS
  Although GPA is an alternative to both IHC and FISH, it may be an unnecessary test for IHC 0/1+/3+ cases. The clinical utility of GPA appears to be similar to other in situ hybridization assays (ie, adjudicator of HER2 status for IHC 2+ cases).
authors.affiliation: From the Magee-Womens Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, and.
authors.forename: Zaibo
authors.initials: Z
authors.lastname: Li
authors.affiliation: From the Magee-Womens Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, and.
authors.forename: David J
authors.initials: DJ
authors.lastname: Dabbs
authors.affiliation: University of Pittsburgh Cancer Institute Biostatistics Facility, Pittsburgh, PA.
authors.forename: Kristine L
authors.initials: KL
authors.lastname: Cooper
authors.affiliation: From the Magee-Womens Hospital of University of Pittsburgh Medical Center, Pittsburgh, PA, and rbhargava@mail.magee.edu.
authors.forename: Rohit
authors.initials: R
authors.lastname: Bhargava
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D040081:Protein Array Analysis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases
keywords: FISH; GPA; HER2 gene; HER2 immunohistochemistry; IHC score 2+