Evaluation of the concordance of ER, PR, HER2, and Ki-67 expression levels between primary breast tumors and their liver metastases: a retrospective analysis of 57 cases

Purpose: This study aims to evaluate the changes in estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67 expression between primary breast tumors and their liver metastases. Materials and methods: A total of 57 patients with breast cancer liver metastases were included. Immunohistochemical staining was performed to assess ER, PR, HER2, and Ki-67 expression in both primary and metastatic tumors. HER2 status was confirmed by silver in situ hybridization (SISH) when necessary. Statistical analyses were conducted to evaluate changes in biomarker expression. Results: Comparison of biomarker expression between primary and metastatic biopsies revealed changes in ER status in 5 cases (1 from negative to positive, 4 from positive to negative); PR status in 22 cases (4 from negative to positive, 18 from positive to negative); HER2 status in 5 cases (2 from negative to positive, 3 from positive to negative); and Ki-67 status in 13 cases (6 from low to high, 7 from high to low). The discordance rates for ER, PR, HER2, and Ki-67 were calculated as 8.8%, 38.6%, 8.8%, and 28.9%, respectively. Conclusion: Our findings confirm that biomarker expression may change between primary and metastatic breast cancer lesions. Given the crucial role of receptor status in treatment decisions, re-biopsy of metastatic lesions is essential to guide personalized therapy.