Challenging the current 1-10% cut-off for defining Estrogen Receptor (ER) Low Positive grade 2-3 ER positive, HER2- early breast cancer

The 2020 ASCO-CAP guidelines recommended ER Low Positive as new reporting category for breast cancers with 1-10% of cells staining ER positive to acknowledge their distinct clinical behaviour compared to breast cancers with >10-100% of tumour cells positive for ER. Dr. Bernard Roobroeck from UZ Leuven presented retrospective data evaluating the prognostic impact of low ER positivity with both 10% and 33% as cut-off.