title: Immunohistochemical and molecular analyses of HER2 status in breast cancers are highly concordant and complementary approaches.
abstract: BACKGROUND
  Immunohistochemistry (IHC) and fluorescent in situ hybridisation (FISH) are currently the most commonly used methods to assess HER2 status. PCR-based assays allow quantitative determination of HER2 amplification (Q-PCR) or overexpression (Q-RT-PCR), but are not routinely used. We evaluated the relevance of Q-RT-PCR for HER2 status determination.
  
  
  METHODS
  We compared IHC and Q-RT-PCR in 466 breast tumours. In discordant or equivocal cases, five additional methods (IHC with two other antibodies, FISH, silver in situ hybridisation (SISH) and Q-PCR) were combined to determine HER2 status. Two cases with HER2 intra-tumour heterogeneity were further explored by allelic profiles analysis and HUMARA clonality determination after microdissection.
  
  
  RESULTS
  We observed 97.3% concordance between Q-RT-PCR and non-equivocal IHC. Twelve out of 466 cases (3%) revealed discordances between the two methods. The power of Q-RT-PCR to predict HER2 status (defined by seven methods) was similar to that of IHC. Although rare, some discordances between techniques might be due to HER2 intra-tumour heterogeneity and we report two examples, one tumour containing two distinct clones, another tumour consisting of HER2 amplified and non-amplified subclones.
  
  
  CONCLUSIONS
  Q-RT-PCR and IHC are highly concordant methods for HER2 status assessment, and Q-RT-PCR allows a highly reliable quantitative assessment and could be a useful adjunct to IHC.
authors.affiliation: AP-HP, Hosp Saint-Louis, Department of Biochemistry, Paris 75010, France. jacqueline.lehmann-che@sls.aphp.fr
authors.forename: J
authors.initials: J
authors.lastname: Lehmann-Che
authors.forename: F
authors.initials: F
authors.lastname: Amira-Bouhidel
authors.forename: E
authors.initials: E
authors.lastname: Turpin
authors.forename: M
authors.initials: M
authors.lastname: Antoine
authors.forename: H
authors.initials: H
authors.lastname: Soliman
authors.forename: L
authors.initials: L
authors.lastname: Legres
authors.forename: C
authors.initials: C
authors.lastname: Bocquet
authors.forename: R
authors.initials: R
authors.lastname: Bernoud
authors.forename: E
authors.initials: E
authors.lastname: Flandre
authors.forename: M
authors.initials: M
authors.lastname: Varna
authors.forename: A
authors.initials: A
authors.lastname: de Roquancourt
authors.forename: L-F
authors.initials: LF
authors.lastname: Plassa
authors.forename: S
authors.initials: S
authors.lastname: Giacchetti
authors.forename: M
authors.initials: M
authors.lastname: Espié
authors.forename: C
authors.initials: C
authors.lastname: de Bazelaire
authors.forename: L
authors.initials: L
authors.lastname: Cahen-Doidy
authors.forename: E
authors.initials: E
authors.lastname: Bourstyn
authors.forename: A
authors.initials: A
authors.lastname: Janin
authors.forename: H
authors.initials: H
authors.lastname: de Thé
authors.forename: P
authors.initials: P
authors.lastname: Bertheau
mesh_terms: D000483:Alleles; D018628:Gene Dosage; D018734:Genes, erbB-2; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D011944:Receptors, Androgen; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*
chemical_list: D011944:Receptors, Androgen