HER2 gene status in primary breast cancers and matched distant metastases

TLDR: Her2 gene status remains highly conserved as breast cancers metastasise, however, discrepant results do occur because of interpretational difficulties and heterogeneity of HER2 amplification.

Abstract: Introduction The status of the gene encoding human EGF-like receptor 2 (HER2) is an important prognostic and predictive marker in breast cancer. Only breast cancers with HER2 amplification respond to the targeted therapy with trastuzumab. It is controversial to what degree the primary tumour is representative of distant metastases in terms of HER2 status. Discrepancies in HER2 status between primary tumours and distant metastases have been described, but their reasons remain unclear. Here, we compared HER2 status on cytological specimens of distant metastases with the result from the primary carcinomas, and explored the prevalence of and the reasons for discrepant results.