MicroRNAs (miRNAs) are a family of highly conserved noncoding single-stranded RNA molecules of 21 to 25 nucleotides. miRNAs silence their cognate target genes at the posttranscriptional level and have been shown to have important roles in oncogenesis, invasion, and metastasis via epigenetic post-transcriptional gene regulation. Recent evidence indicates that the expression of miR-181a is altered in breast tumor tissue and in the serum of patients with breast cancer. However, there are several contradicting findings that challenge the biological significance of miR-181a in tumor development and metastasis. In fact, some studies have implicated miR-181a in regulating breast cancer gene expression. Here we summarize the current literature demonstrating established links between miR-181a and human breast cancer with a focus on recently identified mechanisms of action. This review also aims to explore the potential of miR-181a as a diagnostic and/or prognostic biomarker for breast cancer and to discuss the contradicting data regarding its targeting therapeutics and the associated challenges. [ABSTRACT FROM AUTHOR]