Abstract
BACKGROUND/OBJECTIVE: Hormone receptor (HR) status is one of the key factors in determining the treatment of breast cancer. Previous studies suggested that HR status may change in metastatic tissue. However, available studies focused mainly on primary biopsies and there are only few trials comparing HR status in the primary tumour and the metastasis using material from complete resection. The aim of the study was to determine the frequency of HR alterations in metastatic breast cancer. MATERIALS AND METHODS: The study retrospectively examines a total of 50 patients who underwent brain, lung, or liver metastasectomy for metastatic breast cancer between January 2000 and January 2019. RESULTS: HR conversion was observed in a total of 30 cases (60.0%), while HER-2/neu (human epidermal growth factor receptor 2) discrepancy surprisingly occurred only in one case (2.0%). A change in immunophenotype occurred in 28% of cases. Triple-negativity was more frequent in brain metastases (p = 0.039). CONCLUSIONS: We have confirmed that HR conversion between the primary tumour and its metastases occurs in a significant number of cases, which has important implications for further treatment decisions.