Effect of neoadjuvant chemotherapy on breast cancer phenotype, ER/PR and HER2 expression - Implications for the practising oncologist

Significant changes in tumour morphology, grade, hormone receptors and HER2 status occur following NACT. We recommend testing on residual invasive carcinoma. A switch from negative to positive status warrants offering endocrine/trastuzumab-based therapy to this group of patients.