1 Ono Ono M M Tsuda Tsuda H H Yoshida Yoshida M M Shimizu Shimizu C C Kinoshita Kinoshita T T Tamura Tamura K K Prognostic significance of progesterone receptor expression in estrogen-receptor positive, HER2-negative, node-negative invasive breast cancer with a low Ki-67 labeling index Prognostic significance of progesterone receptor expression in estrogen-receptor positive, HER2-negative, node-negative invasive breast cancer with a low Ki-67 labeling index Clin Breast Cancer Clin Breast Cancer 2017 2017 17 17 41 41 47 47 10.1016/j.clbc.2016.06.012 10.1016/j.clbc.2016.06.012 27477822 27477822. The gene discussed is ESR1; the disease is breast cancer.