ESR1 and breast cancer: BreastOncPx is a 14-gene signature assay (BUB1, CCNB1, CENPA, DC13, DIAPH3, MELK, MYBL2, ORC6L, PKMYT1, PRR11, RACGAP1, RFC4, TK1, UBE2S) that provides prognostics information for lymph node-negative, ER+ BC patients and is associated with risk of distant metastasis.