ESR1 and ductal breast carcinoma in situ: The independent data consisted of 8 cases of HER2-positive breast cancer and 24 cases of HER2-negative breast cancers composed of 8 benign breast lesions defined as free of DCIS or invasive cancer, 8 ER+ (estrogen receptor positive) cases, and 8 cases of triple negative breast cancer (TN, estrogen receptor negative, progesterone receptor negative and HER2 negative) [18].