ESR2 and breast cancer: When we analyzed breast cancer cases of the basal-like intrinsic subtype [12] using the same approach, we additionally observed a strong association of higher ERβ mRNA levels with prolonged RFS (HR = 0.64 (0.5–0.82), log rank p = 0.00051), with an upper quartile relapse-free survival of the low expression cohort of 17.76 months, compared to a survival of 30.6 months in the high expression cohort (data not shown).