Discordance and clinical significance of ER, PR, and HER2 status between primary breast cancer and synchronous axillary lymph node metastasis

Discordance of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status between primary breast cancer, metastatic lesion and synchronous axillary lymph node metastasis has been reported in the series studies. Systemic treatment of primary invasive breast cancer patients with synchronous axillary metastasis is currently based on the biomarker characteristics of the primary tumor; however, hormone receptors and HER2 status may change throughout tumor progression from the primary tumor to the synchronous axillary metastasis. As local metastasis, the synchronous axillary lymph node metastasis may represent the potentially metastatic breast cancer cells much better than the primary tumor. Hence, the determination of hormone receptors and HER2 status should be routinely performed in synchronous axillary nodal metastasis, together with primary tumor, to guide therapy management and evaluate the recurrent risk of primary invasive breast cancer patients with synchronous axillary nodal metastasis, which may even change the postoperative risk categories (St. Gallen consensus) of breast cancer in these patients. This article will review the studies on the discordance and clinical significance of ER, PR, and HER2 receptor status between primary breast cancer and synchronous axillary lymph node metastasis.