Discordance in Hormone Receptor and HER2 Status Between Primary Breast Cancer and Synchronous Ipsilateral Axillary...

Molecular biomarkers are critical for the management of breast cancer, with immunohistochemical analysis of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) guiding treatment decisions. This study aims to evaluate discordance rate in ER, PR, and HER2 between primary breast cancer and ipsilateral synchronous axillary node metastases. A prospective analytical study was conducted at a tertiary medical college, over 1 year (December 2023 to December 2024). We analyzed 50 cases of breast carcinoma with positive axillary lymph node metastasis. Immunohistochemistry for ER, PR, and HER2 was performed on both primary tumors and axillary lymph nodes. The mean age of participants was 54 years. Concordance rates were 86% for ER, 88% for PR, and 91% for HER2. Discordance rates were 14% for ER, 12% for PR, and 9% for HER2. Notably, 4% of cases showed ER positive in primary tumors and ER negative in lymph nodes, while 10% demonstrated the opposite. This study reveals significant discordance in biomarker expression between primary breast cancer and synchronous axillary lymph nodes, underscoring the heterogeneity of breast cancer. Clinically, such discordance could lead to suboptimal treatment if decisions are based solely on primary tumor profiling. These findings highlight the potential benefit of evaluating metastatic sites when formulating treatment strategies. Further research with larger cohorts is warranted to confirm these observations and better define their impact on personalized cancer care.