Tamoxifen [1-(p-dimethylaminoethoxyphenyl)-1,2-diphenyl-1-butene], a selective estrogen receptor (ER) modulator, has been widely used for the treatment and prevention of recurrence for patients with hormone receptor (ER or progesterone receptor)-positive breast cancers in more than 120 countries throughout the worldwide [4]. Here, ESR1 is linked to breast carcinoma.