[Consensus on clinical diagnosis and treatment of breast cancer with low expression and ultralow expression of HER-2 (2025 edition)].

The treatment of breast cancer with low expression of human epidermal growth factor receptor 2 (HER-2) has become a focused area in recent years. With the proved therapeutic effect of antibody-drug conjugates on breast cancer patients with HER-2-low expression, this subgroup has become a new targeting population in breast cancer. Recent studies have shown that patients with HER-2-ultralow breast cancer can also benefit from novel antibody-drug conjugates. To better standardize the rational clinical diagnosis and treatment of HER-2-low and HER-2-ultralow breast cancer, the Breast Cancer Professional Committee of China Anti-Cancer Association, along with Breast Cancer Prevention and Treatment Research Professional Committee of Maternal and Child Health Research Society of China reviewed the latest domestic and international clinical studies and important publications in recent years. Integrating the clinical experience of Chinese pathologists and oncologists, and following expert panel discussions, a consensus on the clinical diagnosis and treatment of HER-2-low and HER-2-ultralow breast cancer was developed. This consensus aims to deepen clinicians' understanding of HER-2-low and HER-2-ultralow breast cancer, promote more precise clinical decision-making, and ultimately improve patient survival and quality of life.