ESR1 and breast cancer: However, the sample size and/or limited molecular characterization of tumor specimens precluded a more in-depth evaluation of specific miRNAs in the context of known molecular biomarkers that impact clinical decisions (e.g., estrogen receptor [ER]/progesterone receptor [PR]/human epidermal growth factor-like receptor 2 [HER2] status in breast cancer; K-Ras and EGFR mutation status in colon and lung cancer).