Among the studies that used IHC, one reported that the relative risk for all-cause mortality, adjusted for tumor size and the percentage of nuclei stained for proliferation-related antigen, was 0.65 (95% CI = 0.30 to 1.43) when comparing patients with >10% with those with ≤10% of ER positively immunostained tumor cell nuclei and was 0.44 (95% CI = 0.21 to 0.93) when comparing >30% with those with ≤30% of ER [26]. Here, ESR1 is linked to neoplasm.