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Open Access Highly Accessed Research article

St Gallen molecular subtypes in primary breast cancer and matched lymph node metastases - aspects on distribution and prognosis for patients with luminal A tumours: results from a prospective randomised trial

Anna-Karin Falck12, Mårten Fernö3, Pär-Ola Bendahl3 and Lisa Rydén14*

Author Affiliations

1 Department of Surgery, Clinical Sciences, Lund University, Lund SE-22185, Sweden

2 Department of Surgery, Hospital of Helsingborg, Helsingborg SE-251 87, Sweden

3 Department of Oncology, Clinical Sciences, Lund University, Lund SE- 22185, Sweden

4 Department of Surgery, Skåne University Hospital, Lund SE-22185, Sweden

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BMC Cancer 2013, 13:558  doi:10.1186/1471-2407-13-558

Published: 25 November 2013

Abstract

Background

The St Gallen surrogate molecular subtype definitions classify the oestrogen (ER) positive breast cancer into the luminal A and luminal B subtypes according to proliferation rate and/or expression of human epidermal growth factor receptor 2 (HER2) with differences in prognosis and chemo-responsiveness. Primary tumours and lymph node metastases might represent different malignant clones, but in the clinical setting only the biomarker profile of the primary tumour is used for selection of adjuvant systemic treatment. The present study aimed to classify primary breast tumours and matched lymph node metastases into luminal A, luminal B, HER2-positive and triple-negative subtypes and compare the distributions.

Methods

Eighty-five patients with available tumour tissue from both locations were classified. The distribution of molecular subtypes in primary tumours and corresponding lymph node metastases were compared, and related to 5-year distant disease-free survival (DDFS).

Results

The St Gallen molecular subtypes were discordant between primary tumours and matched lymph node metastases in 11% of the patients (p = 0.06). The luminal A subtype in the primary tumour shifted to a subtype with a worse prognostic profile in the lymph node metastases in 7 of 45 cases (16%) whereas no shift in the opposite direction was observed (0/38) (p = 0.02). All subtypes had an increased hazard for developing distant metastasis during the first 5 years after diagnosis in both primary breast tumours and matched lymph node metastases, compared with the luminal A subtype.

Conclusion

The classification according to the St Gallen molecular subtypes in primary tumours and matched lymph node metastases, implicates a shift to a more aggressive subtype in synchronous lymph node metastases compared to the primary breast tumour. The selection of systemic adjuvant therapy might benefit from taking the molecular subtypes in the metastatic node into account.

Keywords:
Breast cancer; Luminal A; Lymph node metastases; Molecular subtypes; Prognosis; Tumour progression