ESR1 and breast cancer: We have also included studies in other breast cancer subtypes, where they analysed miRNAs targeting one of the three receptors (ER, PR, HER2, i.e., miRs targeting these receptors may be responsible for the lack of receptor expression in TNBC) or those miRs associated with metastasis in other breast cancer subtypes, since these studies may allow us to gain further insight into miRNAs that may be involved in TNBC.