This multicenter, real-world, observational study will retrospectively and prospectively collect real-world data related to the investigational drugs. We plan to observe 1000 patients and collect data on treatment cycles N and N+1 of the targeted therapies. Retrospective data collection is based on existing patient diagnosis and treatment records, collecting information on patients who have completed two treatment cycles before January 1, 2024. Prospective data collection is based on routine clinical treatment during the study period, collected until the end of the next cycle of treatment or early termination of the study. To observe the disease characteristics and management mode of hematological toxicity related to targeted therapies of breast cancer, and explore the possible related factors of hematological toxicity, such as age, disease subtype, cancer stage, targeted therapy regimens, etc. This study will respect the medication choices of researchers in the study, without specifying which medication to choose for treatment, dosage, mode of administration (including single drug, combination therapy, or sequential therapy), and duration of administration.