ERBB2 and breast cancer: Unfortunately, high frequency of TAM resistance remains a risk for metastasis and progression of ER+ breast cancers.3, 4 Breast cancer stem cells (BCSCs) are thought to be critical players for drug resistance.5, 6 BCSCs can regulate the sensitivity of breast cancer cells to TAM by modulating the NF‐κB, PI3K/PTEN/AKT/mTOR, β‐catenin and HER2 pathways.7, 8 Therefore, reducing the frequency of BCSCs and inhibiting their function will be valuable for control of TAM resistance.