Breast cancer remains the most common malignancy among women, with persistently high incidence and mortality rates. Its heterogeneity, drug resistance, and the toxicity associated with conventional therapies continue to challenge clinical management.In recent years, rare-earth-doped upconversion nanoparticles (UCNPs) have attracted growing attention in breast cancer research owing to their unique optical properties, tunable synthesis, and flexible functionalization strategies.Recently, the research teams led by Professor Xiaoyun Mao from the First Affiliated Hospital of China Medical University and Professor Wen Xu from the School of Physics and Materials Engineering, Dalian Minzu University, published a cover review in Theranostics titled 'Engineered Upconversion Nanoparticles for Breast Cancer Theranostics.'This review systematically summarizes the progress of UCNP-based strategies in breast cancer diagnosis and therapy, while also discussing challenges in clinical translation and future development directions.

Editor’s Note: With the expanding role of neoadjuvant therapy in breast cancer, pathologic complete response (pCR) has become an important indicator for evaluating treatment efficacy. Whether patients who achieve pCR…