ESR1 and breast cancer: Concerned about the established inverse relationship between the ER status and poor-risk biomarker surrogates of breast cancer proliferation and genomic instability [13,18], the present study aimed to identify genomic and transcriptome changes associated with aging using DNA and RNA prospectively collected from stage-matched and histology-matched ER-positive breast cancers from younger women (age ≤ 45 years) and older women (age ≥ 70 years), analyzed by array CGH and high-throughput expression microarrays.