Using the gene expression profiles of ER+ breast cancer samples, integrated from three datasets (GSE19615, GSE43365, GSE31448) measured by the Affymetrix’s microarray platform (Table 1 and Supplementary Table S3), we identified 1,442,839 significantly stable gene pairs, each of which had a stable REO in the 105 metastasis samples and a reversely stable REO in the 101 non-metastasis samples (Binomial test, FDR < 0.05). Here, ESR1 is linked to breast cancer.