Main signaling pathways modulated by miRNAs in bCSC. Stem cell maintenance is complex and highly regulated processes, several pathways are essential for the maintenance of bCSC, including NF-κB, PI3K/AKT/mTOR, Notch, Hedgehog, Wnt, Hippo, JAK/STAT, TGF-β, and signaling estrogen receptor-mediated. Deregulation of these pathways can be one of the main reasons for the appearance or exacerbation of the main hallmarks such as maintenance, self-renewal, tumor resistance, relapse, recurrence, aggressiveness, and metastasis of bCSC, among others. Some targets modulated by miRNAs: Wnt, stearoyl desaturase 1 (SCD1), Adenomatous polyposis coli (APC), Lin28; Notch, Jagged2; PI3K//AKT/mTOR, phosphatase and tensin homolog (PTEN) programmed cell death ligand 1 (PD-L1), and TGF-β, SMAD 2-4.