To identify human breast cancer biomarkers between ERα(+) and ERα(−) breast tumors, tissues were microdissected and differential protein expression by adjacent tissues was identified [3], microdissected breast tissues composed of either normal ductal epithelium or ductal epithelium containing Ductal Carcinoma in situ (DCIS) lesions were also compared [4]. Here, ESR1 is linked to ductal breast carcinoma in situ.