HER2/neu, Topoisomerase 2a, Estrogen and Progesterone Receptors: Discordance between Primary Breast Cancer and Metastatic Axillary Lymph Node in Expression and Amplification Characteristics.

Molecular classification of breast cancer (BC) and the evaluation of new biological markers such as estrogen receptor (ER), progesterone receptor (PR), ErbB2 (HER2) and topoisomerase 2a (Topo2a) status are claimed to be important parameters in the management of BC therapy. In case of heterogeneity between primary BC and metastatic site, this implies profound limitations of efficient systemic therapy. Therefore, it is essential to analyze whether biological markers of BC relate to identical expression profiles of metastatic lymph nodes (mLNs). We used paraffin-embedded tumor tissue from 119 patients with at least 1 mLN. Immunohistochemistry (IHC) was used to analyze ER, PR, HER2 and Topo2a. In addition, HER2 and Topo2a amplification was evaluated by fluorescence/chromogenic in situ hybridization (FISH/CISH) in all samples with a HER2 score of 2+/3+ by IHC. Overall, the percentage of discordant marker status in the BC and its mLN was 2.6% for ER, 3.5% for PR, 3.4% for HER2, and 3.4% for Topo2a. With FISH/CISH, the amplification rate for Topo2a and HER2 was concordant in all cases. Because there are no prospective studies, it remains unclear whether these discrepancies have an effect on patient survival.

Prospective multi-centre study to validate chromogenic in situ hybridisation for the assessment of HER2 gene amplification in specimens from adjuvant and metastatic breast cancer patients.

PURPOSE: As HER2 status is a strong predictor of the response to trastuzumab, clinical guidelines recommend that all breast tumours are first evaluated for HER2 protein expression by immunohistochemistry (IHC) followed by confirmatory testing for HER2 gene amplification using fluorescence in situ hybridisation (FISH) for 2+ cases. Alternatively, chromogenic in situ hybridisation (CISH) offers a simpler, less expensive approach to detect HER2 amplification. METHODS: In this prospective, multi-centre study, based on the largest dataset for HER2 testing in Germany to date, we evaluated the concordance between FISH and CISH in 399 samples from adjuvant and metastatic breast cancer patients. Tumour specimens from routine diagnostic practice were analysed by IHC, FISH and CISH in four reference centres. RESULTS: FISH and CISH results were strongly concordant (κ = 0.83), with 95% of cases showing agreement. Despite variable IHC scoring across testing centres, complete consensus among the three methods was observed for 246 cases, representing 91% of all IHC positive (3+) or negative (0/1+) cases. Confirmatory testing of 132 IHC equivocal (2+) cases also yielded highly concordant results between FISH and CISH. CONCLUSIONS: These data validate CISH for the assessment of HER2 gene amplification in breast tumours and, confirm CISH as a valid alternative to FISH in HER2 testing.