Research conducted over the past decade on the distribution of miRNA expression profiles in breast cancer and the search for a correlation with clinical outcomes as well as molecular targets of miRNAs have allowed the identification of miRNAs signatures linked to pivotal breast cancer processes like tumor size, lymph node metastasis, and status of hormones receptors as well as to inflammation and obesity. This evidence concerns the gene NR4A1 and obesity due to melanocortin 4 receptor deficiency.