1. ¹Oncology Unit, Sieff Government Hospital, Safed, Israel
2. ²Faculty of Medicine, Israel Institute of Technology (Technion), Haifa, Israel
3. ³Department of Surgery, Sieff Government Hospital, Safed, Israel
4. ⁴Department of Pathology, Sieff Government Hospital, Safed, Israel

Correspondence: Dr J Zidan, E-mail: zidan.j@ziv.health.gov.il

Received 11 January 2005; Revised 19 May 2005; Accepted 13 July 2005; Published online 16 August 2005.

Abstract

HER-2 overexpression, a predictive marker of tumour aggressiveness and responsiveness to therapy, occurs in 20–30% of breast cancer. Although breast cancer is a heterogeneous disease, HER-2 measurement is carried out in primary tumour. This study aims to evaluate HER-2 overexpression in primary and metastases and its effect on treatment decisions. Biopsies from primary breast cancer and corresponding metastases from 58 patients were studied. HER-2 overexpression was evaluated immunohistochemically in all primary and metastatic sites. Positive overexpression in primary and/or metastases was confirmed by fluorescence in situ hybridisation (FISH). Discordance in HER-2 overexpression between primary and metastatic sites was 14% (eight of 58 patients). Concordance was found in 50 (86%) of patients (95% CI: 77–95). In one patient (2%), HER-2 was negative in metastasis but positive in primary. In seven (12%) patients, HER-2 was positive in metastases and negative in primary (95% CI: 3.7–20), and three of them responded to trastuzumab. Gene amplification by FISH was found in all cases with HER-2 positive (+2 and +3) by immunohistochemistry. Our data suggest that a possible discordance of HER-2 overexpression between primary and metastases should be considered when making treatment decisions in patients with primary HER-2-negative tumours.