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Triple negative breast cancer: a study from the point of view of basal CK5/6 and HER-1
  1. S Pintens1,
  2. P Neven2,
  3. M Drijkoningen1,
  4. V Van Belle3,
  5. P Moerman1,
  6. M-R Christiaens4,
  7. A Smeets4,
  8. H Wildiers5,
  9. I Vanden Bempt1
  1. 1
    Department of Pathology, UZ Leuven, Leuven, Belgium
  2. 2
    Department of Gynecological Oncology, UZ Leuven, Catholic University Leuven, Leuven, Belgium
  3. 3
    Department of Electrical Engineering (ESAT), KU Leuven, Leuven, Belgium
  4. 4
    Department of Surgery, UZ Leuven, Leuven, Belgium
  5. 5
    Department of Medical Oncology, UZ Leuven, Leuven, Belgium
  1. ProfessorDr Patrick Neven, Multidisciplinary Breast Centre and Gynecological Oncology, University Hospital KU Leuven, Herestraat 49, B-3000 Leuven, Belgium; patrick.neven{at}


Aim: Basal-like breast tumours, as defined by microarrays, carry a poor prognosis and therapeutic options are limited to date. Often, these tumours are defined as oestrogen receptor (ER) negative/progesterone receptor (PR) negative/human epidermal growth factor receptor 2 (HER-2) negative (triple negative) by immunohistochemistry (IHC), but a more complete definition should include expression of basal cytokeratins (CK5/6, CK14 or CK17) and/or human epidermal growth factor receptor 1 (HER-1). The aim of this study was to investigate to what extent CK5/6 and HER-1 characterise the group of triple negative breast cancers.

Methods: Expression of CK5/6 and HER-1 was studied by IHC in 25 triple negative breast carcinomas and 32 grade-matched, non-triple-negative controls. All 57 cases were further subjected to fluorescence in situ hybridisation to investigate HER-1 gene copy number.

Results: CK5/6 and HER-1 expression was most frequent in triple negative tumours: 22 out of 25 cases (88.0%) expressed at least one of these markers (60.0% CK5/6 positive and 52.0% HER-1 positive). In the control group, CK5/6 and HER-1 expression was found in ER-negative but not in ER-positive tumours (ER negative/PR negative/HER-2 positive tumours: 20.0% CK5/6 positive and 46.7% HER-1 positive). HER-1 gene amplification was found in five cases only: four triple negative (16.0%) and one ER-negative control (ER negative/PR negative/HER-2 positive, 6.7%). Of interest, all five HER-1 amplified cases showed a remarkably homogeneous HER-1 expression pattern.

Conclusion: Expression of CK5/6 and HER-1 is frequent in ER-negative breast cancers, in triple negative and in non-triple negative tumours. In a minority of cases, HER-1 overexpression may be caused by HER-1 gene amplification. Further studies are needed to investigate whether such cases might benefit from anti-HER-1 therapy

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  • Competing interests: None.