title: Patterns of her-2/neu amplification and overexpression in primary and metastatic breast cancer.
abstract: BACKGROUND
  Only 25% of patients with HER-2/neu-positive metastatic breast tumors respond favorably to trastuzamab (Herceptin) treatment. We hypothesized that a high failure rate of patients on trastuzamab could result if some of the metastases were HER-2 negative and these metastases ultimately determine the course of the disease.
  
  
  METHODS
  We used tissue microarrays (TMAs) containing four samples each from 196 lymph node-negative primary tumors, 196 lymph node-positive primary tumors, and three different lymph node metastases from each lymph node-positive tumor to estimate HER-2 gene amplification by fluorescence in situ hybridization (FISH) and Her-2 protein overexpression by immunohistochemistry (IHC).
  
  
  RESULTS
  FISH and IHC analyses gave the same result with respect to HER-2 status for 93.7% of the tissues contained in the TMAs. Tissue samples were, therefore, considered to be HER-2 positive if they were positive for either HER-2 DNA amplification or Her-2 protein expression and HER-2 negative if both FISH and IHC gave a negative result. The HER-2 status of lymph node-positive primary tumors was maintained in the majority of their metastases. For HER-2-positive primary tumors, 77% (95% confidence interval [CI] = 59% to 90%) had entirely HER-2-positive metastases, 6.5% (95% CI = 8% to 21%) had entirely HER-2-negative metastases, and 16.3% (95% CI = 5% to 34%) had a mixture of HER-2-positive and HER-2-negative metastases. For HER-2-negative primary tumors, 95% (95% CI = 88% to 98%) had metastases that were entirely negative for HER-2.
  
  
  CONCLUSIONS
  Our data suggest that differences in HER-2 expression between primary tumors and their lymph node metastases cannot explain the high fraction of nonresponders to trastuzamab therapy.
authors.affiliation: Institute of Pathology, University of Basel, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Simon
authors.forename: A
authors.initials: A
authors.lastname: Nocito
authors.forename: T
authors.initials: T
authors.lastname: Hübscher
authors.forename: C
authors.initials: C
authors.lastname: Bucher
authors.forename: J
authors.initials: J
authors.lastname: Torhorst
authors.forename: P
authors.initials: P
authors.lastname: Schraml
authors.forename: L
authors.initials: L
authors.lastname: Bubendorf
authors.forename: M M
authors.initials: MM
authors.lastname: Mihatsch
authors.forename: H
authors.initials: H
authors.lastname: Moch
authors.forename: K
authors.initials: K
authors.lastname: Wilber
authors.forename: A
authors.initials: A
authors.lastname: Schötzau
authors.forename: J
authors.initials: J
authors.lastname: Kononen
authors.forename: G
authors.initials: G
authors.lastname: Sauter
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000556:secondary; D018275:Carcinoma, Lobular / Q000235:genetics / Q000556:secondary; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D018734:Genes, erbB-2 / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008207:Lymphatic Metastasis; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D000068878:Trastuzumab; D015854:Up-Regulation
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D000068878:Trastuzumab