Receptor Discordance between Primary and Recurrent Breast Cancer: A Systematic Literature Review

Breast cancer is the most common cancer among women, with hormone receptors playing a crucial role, not only in cancer cell growth but also as primary targets in breast cancer treatment. This systematic literature review aimed to summarize the current evidence on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) discordance rates between primary and recurrent breast cancer. Additionally, it seeks to identify how discordance affects prognosis, metastasis, and the potential evidence of primary tumor heterogeneity.