ESR1 and neoplasm: Notably, in ER negative tumours that were negative for the basal-cell marker CK5/6 (n = 53), stathmin alone predicted BRCA1 status (p = 0.004), whereas none of the markers (stathmin, mitotic count, p53) could predict BRCA1 status in ER negative, CK5/6 positive tumours (n = 35).