CSCs are the root cause of drug resistance and treatment failure.19, 20 The mechanisms of drug resistance in CSCs include overexpression of ATP‐binding cassette transporters, over‐activation of cell detoxification enzymes, abnormal activation of cell survival and apoptosis‐related signal transduction pathways, the protective effect of tumour niches on tumour stem cells, and that most CSCs are in a quiescent phase.21, 22, 23 By intervening in these processes, we may reverse resistance to trastuzumab and improve the survival and prognosis of breast cancer patients. This evidence concerns the gene ABCA4 and neoplasm.