title: Distinguishing score 0 from score 1+ in HER2 immunohistochemistry-negative breast cancer: clinical and pathobiological relevance.
abstract: OBJECTIVE
  To investigate the clinical and pathobiological significance of distinguishing score 0 and score 1+ within the group of immunohistochemistry (IHC)-negative invasive breast cancers.
  
  
  METHODS
  We studied HER2 status using both IHC and fluorescence in situ hybridization (FISH) in 150 consecutive breast tumors submitted to our laboratory after a negative IHC result in local testing centers.
  
  
  RESULTS
  We were able to discern a group of score 0 tumors that had a lower HER2 copy number than the group consisting of score 1+ tumors. In contrast with the group of score 1+ tumors, HER2 FISH was consistently negative for both copy number-based and ratio-based tumors without equivocal results.
  
  
  CONCLUSIONS
  In a setting with stringent quality assurance, score 0 and score 1+ tumors emerge as distinct and clinically important subgroups within the HER2 IHC-negative population.
authors.affiliation: Dept of Pathology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium; e-mail: kathleen.lambein@ugent.be.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Lambein
authors.forename: Mieke
authors.initials: M
authors.lastname: Van Bockstal
authors.forename: Lies
authors.initials: L
authors.lastname: Vandemaele
authors.forename: Sofie
authors.initials: S
authors.lastname: Geenen
authors.forename: Isabelle
authors.initials: I
authors.lastname: Rottiers
authors.forename: Ann
authors.initials: A
authors.lastname: Nuyts
authors.forename: Bart
authors.initials: B
authors.lastname: Matthys
authors.forename: Marleen
authors.initials: M
authors.lastname: Praet
authors.forename: Hannelore
authors.initials: H
authors.lastname: Denys
authors.forename: Louis
authors.initials: L
authors.lastname: Libbrecht
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D018270:Carcinoma, Ductal, Breast / Q000145:classification / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D005260:Female; D018628:Gene Dosage; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods* / Q000592:standards; D017404:In Situ Hybridization, Fluorescence; D008408:Mastectomy; D011785:Quality Assurance, Health Care; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: Breast cancer; FISH; HER2; Immunohistochemistry; Score 0; Score 1+