In order to identify the miRNAs which contribute to the metastases of human breast cancers, microarray data representing the ESR1(+)/ERBB2(-) breast cancer specimens from 54 patients was retrieved from Gene Expression Omnibus (GEO, accession GSE59829)15 so as to compare the expression levels of miRNAs of specimens between the patients with or without metastasis. Here, ESR1 is linked to breast cancer.