Recently, Lidfeldt et al. provided a novel insight into the respective role of PAR1 and PAR2 in human breast cancer by showing that PAR2 was confined to the estrogen receptor (ER)-positive sub-group and PAR2 was an independent prognostic factor specifically in ER-positive tumors, while PAR1 correlated with worse prognosis specifically with ER-negative group [288]. This evidence concerns the gene ESR1 and breast cancer.