A contemporary study focusing on the small RNA sequencing of 186 breast tumor samples from the SCAN-B initiative identified 684 microRNAs per sample, which, upon clustering, led to the identification of signatures of differentially expressed miRNAs associated with 10 intrinsic subtypes (HER2, HER2-Basal, HER2-LumA, HER2-LumB, Basal, Basal-LumA, Basal-LumB, LumA, LumB and LumA-LumB) [12] and 73 unique microRNAs related to four well-defined clusters that segregated the ER+ luminal tumors from ER- Basal-like and most HER2-enriched tumors [12]. This evidence concerns the gene ESR1 and breast neoplasm.