ESR1 and breast carcinoma: Certain studies have demonstrated that the reduced ERα phosphorylation at serine 118 (pERα-S118) and the increased ERα phosphorylation at serine 167 (pERα-S167) were correlated significantly with the improved disease-free survival (DFS) and overall survival (OS) of breast cancer patients, while alternative studies have suggested a correlation between either pERα-S118 or pERα-S167 and tamoxifen resistance (5).