Intervention: Disitamab vedotin (RC48-ADC), an antibody–drug conjugate (targeted immunotherapy). Mechanism: a humanized anti‑HER2 monoclonal antibody delivers the cytotoxic payload MMAE via a cleavable linker. After binding HER2 (ERBB2) on tumor cells and internalization, MMAE is released to disrupt microtubules, causing G2/M arrest and apoptosis, a bystander effect and Fc‑mediated ADCC may contribute. Targets: HER2‑expressing breast cancer cells, microtubule cytoskeleton (direct payload target), immune effector pathways via Fcγ receptors (NK cells/macrophages) for ADCC, HER2/ERBB2 axis (PI3K/AKT/MAPK) is addressed via antigen targeting. Real‑world observational study, typical dosing 2.0 mg/kg IV every 2 weeks.