The data-driven optimal cutpoints for the PM2000/AQUA platform-derived data revealed a population of estrogen receptor-positive patients, whose tumors constituted the lowest 21% of Nuc-pYStat5-expressing tumors, and who were at a 3.7-fold increased risk of breast cancer recurrence (hazard ratio 3.74 (1.62–8.63), P=0.002, N=193; Figure 2a). This evidence concerns the gene ESR1 and breast cancer.