MicroRNAs (miRNAs) play a significant role in numerous biological processes and are implicated in a range of cancers, including breast cancer. MiRNAs have the potential to be biomarkers in clinical practice because of their distorted and unique expression, especially with regard to their presence in cancer stem cells (CSCs) that have applications in cancer diagnosis and treatment. Thus, the absolute determination of miRNA expression levels is a prerequisite for exploring their applications.