ESR1 and ovarian cancer: However, these studies are associated with the following limitations: The cut-off levels for ER and PR negativity were not specified or defined as nuclear staining of ≤10% (12,13), neither group was homogenized by received chemotherapy regimens (7), missing information with regard to accompanying cancers or patients with previous ovarian cancer were not included in the study (7,13), breast cancer-specific survival (BCS) rates were not evaluated (7) and the prognostic significance of separate BRCA1 mutations were also not evaluated (7,12,13).