To address this question, our study aimed to compare the relapse-free survival (RFS) and OS of HER2-low tumours with HER2-zero tumours by hormone receptor status and by HER2 IHC 0, 1+ and 2+ ISH− status in a large multicentre cohort of non-metastatic BC patients. The gene discussed is NR4A1; the disease is neoplasm.