ESR1 and breast cancer: Tumors from 104 patients with primary breast cancer who received adjuvant tamoxifen therapy at The Affiliated Cancer Hospital of Shantou University Medical College between January 2001 to December 2007 were subjected to immunohistochemical analysis with specific antibodies against ERα phosphorylated at either serine 118 (pERα-S118) and/or serine 167 (pERα-S167).