To address the need for a tool to monitor Notch signalling, we describe in this report the identification of a 20-gene Notch transcriptomic signature (NRARP, SEMA5B, PLAT, PRELP, HEYL, FAT2, HEY1, NPR3, KRT5, FLT1, KRT14, RHOV, TNFRSF19, JAG1, MT1X, HEY2, PDGFRB, ZNF469, VSNL1 and KIT), which shows a very robust coherence score for breast cancer. The gene discussed is HEY1; the disease is breast cancer.