ESR1 and breast cancer: MSigDB c3 contains a target gene list for ER named V$ER_Q6_01, for which it was reasoned that a statistically significant, favorable prognosis should be observed in ER+ tumors and no prognostic implications observed for ER- tumors, given that standard breast cancer hormonal therapy targets the ER pathway to great effect and the pathway would be inactive in ER- tumors.