ORIGINAL ARTICLES

HER-2/neu analysis in breast cancer bone metastases

J Zustin¹, K Boddin¹, M C Tsourlakis¹, E Burandt¹, M Mirlacher¹, F Jaenicke², J Izbicki³, W Ruether⁴, J M Rueger⁵, C Bokemeyer⁶, R Simon¹, G Sauter¹

¹ Institute of Pathology, University Medical Center Hamburg-Eppendorf, Germany
² Department of Gynecology, University Medical Center Hamburg-Eppendorf, Germany
³ Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, Germany
⁴ Department of Orthopaedics, University Medical Center Hamburg-Eppendorf, Germany
⁵ Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Germany
⁶ II. Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, Germany

Correspondence to:
Dr J Zustin, Institute of Pathology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany; j.zustin{at}uke.uni-hamburg.de

Background: HER-2 is the target for antibody-based treatment of breast cancer (trastuzumab), which is highly successful in both advanced disease and the adjuvant setting. HER-2 can be analysed by fluorescence in situ hybridisation (FISH) for gene amplification or immunohistochemistry (IHC) for protein overexpression.

Aim: As both methods are known to be influenced by previous tissue processing, to analyse the applicability of both FISH and IHC to decalcified bone metastases of breast cancer.

Methods: A tissue microarray (TMA) was constructed from 149 breast cancer bone metastases. Consecutive TMA sections were analysed by FISH (PathVysion) and IHC (HercepTest).

Results: FISH analysis was interpretable in 113 (85.0%) cases. Amplification was seen in 14 (12.4%) interpretable metastases. HER-2 positivity on IHC analysis was 3+ in 9.8% of cases and 2+ in 11.3%. A comparison of the two techniques revealed high concordance. Of the 14 cases of amplification, 10 (71%) showed 3+ IHC staining, two (14%) showed 2+, one (7%) showed 1+, and one (7%) showed 0+. Three of the four amplified cases that did not show 3+ IHC staining had an equivocal FISH result, with a HER-2/centromere 17 ratio of 1.8–2.2. Of the 13 cases that showed IHC 3+ staining, amplification was present in 10 (77%).

Conclusions: HER-2 FISH analysis has an excellent success rate in highly standardised EDTA-decalcified bone metastases, suggesting that this method is easily applicable to decalcified tissues. The high concordance between IHC and FISH suggests that HER-2 IHC may be equally applicable to EDTA-treated tissues as to the usual formalin-fixed tissues.

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