title: Interlaboratory comparison of immunohistochemical testing for HER2: results of the 2004 and 2005 College of American Pathologists HER2 Immunohistochemistry Tissue Microarray Survey.
abstract: BACKGROUND
  Correct assessment of human epidermal growth factor receptor 2 (HER2) status is essential in managing patients with invasive breast carcinoma, but few data are available on the accuracy of laboratories performing HER2 testing by immunohistochemistry (IHC).
  
  
  OBJECTIVE
  To review the results of the 2004 and 2005 College of American Pathologists HER2 Immunohistochemistry Tissue Microarray Survey.
  
  
  METHODS
  The HER2 survey is designed for laboratories performing immunohistochemical staining and interpretation for HER2. The survey uses tissue microarrays, each consisting of ten 3-mm tissue cores obtained from different invasive breast carcinomas. All cases are also analyzed by fluorescence in situ hybridization. Participants receive 8 tissue microarrays (80 cases) with instructions to perform immunostaining for HER2 using the laboratory's standard procedures. The laboratory interprets the stained slides and returns results to the College of American Pathologists for analysis. In 2004 and 2005, a core was considered "graded" when at least 90% of laboratories agreed on the result--negative (0, 1+) versus positive (2+, 3+). This interlaboratory comparison survey included 102 laboratories in 2004 and 141 laboratories in 2005.
  
  
  RESULTS
  Of the 160 cases in both surveys, 111 (69%) achieved 90% consensus (graded). All 43 graded cores scored as IHC-positive were fluorescence in situ hybridization-positive, whereas all but 3 of the 68 IHC-negative graded cores were fluorescence in situ hybridization-negative. Ninety-seven (95%) of 102 laboratories in 2004 and 129 (91%) of 141 laboratories in 2005 correctly scored at least 90% of the graded cores.
  
  
  CONCLUSIONS
  Performance among laboratories performing HER2 IHC in this tissue microarray-based survey was excellent. Cores found to be IHC-positive or IHC-negative by participant consensus can be used as validated benchmarks for interlaboratory comparison, allowing laboratories to assess their performance and determine if improvements are needed.
authors.affiliation: Department of Pathology, St Jude Medical Center, Fullerton, Calif, USA.
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Fitzgibbons
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Murphy
authors.forename: David M
authors.initials: DM
authors.lastname: Dorfman
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Roche
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Tubbs
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology*; D003625:Data Collection; D005260:Female; D018734:Genes, erbB-2; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D017404:In Situ Hybridization, Fluorescence; D007753:Laboratories / Q000592:standards*; D009361:Neoplasm Invasiveness; D020411:Oligonucleotide Array Sequence Analysis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D015203:Reproducibility of Results; D013194:Staining and Labeling
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases