The quantitative real-time polymerase chain reaction (qRT-PCR)-derived “ER gene (ER-ness) score” for the expression of the ESR1 gene and downstream gene targets (ESR1, GATA3, TFF1) was confirmed to be an accurate predictor of the ER status in ER low-status tumor samples [32,35]. This evidence concerns the gene TFF1 and neoplasm.