This project aims to investigate the role of MMA in breast cancer. To this end, we will measure MMA on serum samples collected at the time of breast cancer diagnosis, to investigate the role of MMA in predicting long-term recurrence risk, response to neoadjuvant chemotherapy, and its association with age and clinical frailty. If the role of baseline serum MMA in therapy resistance and/or metastasis is confirmed, our study could be further extended by evaluating SOX4 expression in the tumor tissues (SOX4 is activated by MMA, and SOX4 induces EMT (epithelial to mesenchymal transition) and the metastasis process.