ERBB2 and breast cancer: The Breast Cancer Test (BCT) score is a quantitative, real-time reverse transcription polymerase chain reaction-based multigene assay including 6 prognostic and 3 reference genes, which predicts the risk of distant recurrences and benefits from adjuvant chemotherapy among HR-positive/HER2-negative (HR + /HER2 −) EBC patients based on data from 906 and 346 Korean breast cancer cohorts, respectively [18–20].