ESR1 and breast cancer: Hence, to evaluate the causal variants at 6q25.1 in the development of breast cancer, we screened the potentially functional variants at 6q25.1 within two genes (ESR1 and CCDC170) and assessed their associations with breast cancer risk in a case-control study including 1,064 breast cancer cases and 1,073 controls in Chinese women in Jiangsu province in eastern China.