title: Gene expression profiling and histopathological characterization of triple-negative/basal-like breast carcinomas.
abstract: BACKGROUND
  Breast cancer is a heterogeneous group of tumors, and can be subdivided on the basis of histopathological features, genetic alterations and gene-expression profiles. One well-defined subtype of breast cancer is characterized by a lack of HER2 gene amplification and estrogen and progesterone receptor expression ('triple-negative tumors'). We examined the histopathological and gene-expression profile of triple-negative tumors to define subgroups with specific characteristics, including risk of developing distant metastases.
  
  
  METHODS
  97 triple-negative tumors were selected from the fresh-frozen tissue bank of the Netherlands Cancer Institute, and gene-expression profiles were generated using 35K oligonucleotide microarrays. In addition, histopathological and immunohistochemical characterization was performed, and the findings were associated to clinical features.
  
  
  RESULTS
  All triple-negative tumors were classified as basal-like tumors on the basis of their overall gene-expression profile. Hierarchical cluster analysis revealed five distinct subgroups of triple-negative breast cancers. Multivariable analysis showed that a large amount of lymphocytic infiltrate (HR = 0.30, 95% CI 0.09-0.96) and absence of central fibrosis in the tumors (HR = 0.14, 95% CI 0.03-0.62) were associated with distant metastasis-free survival.
  
  
  CONCLUSIONS
  Triple-negative tumors are synonymous with basal-like tumors, and can be identified by immunohistochemistry. Based on gene-expression profiling, basal-like tumors are still heterogeneous and can be subdivided into at least five distinct subgroups. The development of distant metastasis in basal-like tumors is associated with the presence of central fibrosis and a small amount of lymphocytic infiltrate.
authors.affiliation: Division of Radiation Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
authors.forename: Bas
authors.initials: B
authors.lastname: Kreike
authors.forename: Marieke
authors.initials: M
authors.lastname: van Kouwenhove
authors.forename: Hugo
authors.initials: H
authors.lastname: Horlings
authors.forename: Britta
authors.initials: B
authors.lastname: Weigelt
authors.forename: Hans
authors.initials: H
authors.lastname: Peterse
authors.forename: Harry
authors.initials: H
authors.lastname: Bartelink
authors.forename: Marc J
authors.initials: MJ
authors.lastname: van de Vijver
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics*; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D003528:Carcinoma, Adenoid Cystic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D066246:ErbB Receptors / Q000378:metabolism; D005784:Gene Amplification; D020869:Gene Expression Profiling; D018734:Genes, erbB-2; D006801:Humans; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D066246:ErbB Receptors