The same group published a series with 465 patients with stage I - III breast cancer, demonstrating that the presence of estrogen receptor gene (ESR1) mRNA was documented in only 24% of tumors that express ER from 1 to 9%, while in tumors with ER above 10% the rate of ESR1 mRNA positivity was 92% (28). Here, ESR1 is linked to breast cancer.