ESR1 and breast cancer: One study reported that there was an increased tumor size for the ER-/PR-/HER2+ and ER-/PR-/HER2- subtypes, however, Foulkes WD proposed that basal-like breast cancers and HER2 positive breast cancer were inherently aggressive and were likely to early metastasize, tumor size might not be related to the prognosis [33, 34].