For example, expression from whole transcriptome RNAseq (wtRNAseq) and microarrays prepared from 57 fresh frozen (FF) breast cancers demonstrated strong correlation (r > 0.9) for many genes, including ESR1 (estrogen receptor), PGR (progesterone receptor) and ERBB2 (HER2 receptor), and established multigene signatures such as EndoPredict and OncotypeDX (r > 0.95) [3]. Here, ESR1 is linked to breast cancer.