In the past decade, with the introduction of precision medicine, the treatment of breast cancer has entered a new era. It now tends towards the de-escalation and individualization of treatment plans, aiming to minimize iatrogenic toxicity while maximizing benefits for patients without compromising survival outcomes. The 21-gene assay evaluates the expression levels of 21 genes associated with breast cancer recurrence and provides a 21-gene recurrence score (RS) to assess the risk of recurrence and potential benefit from chemotherapy in breast cancer patients. Currently, RS is recommended by multiple guidelines such as the American Society of Clinical Oncology (ASCO), National Comprehensive Cancer Network (NCCN), and Chinese Anti-Cancer Association(CACA) for guiding adjuvant therapy in hormone receptor-positive (HR⁺) and human epidermal growth factor receptor 2 negative (HER2^-) early-stage breast cancer patients. However, there are still controversies surrounding its clinical application. Current research mainly focuses on optimizing RS to accurately identify patients who would benefit from adjuvant therapy, thus enabling more personalized treatment plans for breast cancer patients. This review provides an overview of the 21-gene assay, its application in HR⁺ breast cancer patients' adjuvant therapy, its impact on clinical decision-making, existing controversies regarding RS, and prospects for integrating RS with clinical pathological information. The aim is to guide further expansion of RS's application in clinical practice and achieve more precise adjuvant therapy for breast cancer patients.

Bone is the most common metastatic site of advanced breast cancer. Bone related events caused by bone metastasis seriously affect the quality of life and survival time of patients. Therefore, in order to improve the quality of life and prolong the survival time of breast cancer patients with bone metastases, it is of great clinical value to investigate the occurrence and development mechanism of bone metastases, explore early diagnosis methods, and pursue abundant and effective treatment methods and drugs for bone metastases. This article mainly reviews the new research progress of bone metastasis of breast cancer from the aspects of molecular mechanism, imaging and biological diagnosis methods, systematic treatment, in order to provide more reference for clinical diagnosis and treatment.