The cohort (n = 439) was classified into four breast cancer subtypes on the basis of hormone receptor (ERα and PR) and ERBB2 status: HR+/ERBB2+ (n = 50), HR+/ERBB2- (n = 281), HR-/ERBB2+ (n = 41) and HR-/ERBB2- (n = 67). Here, ESR1 is linked to breast carcinoma.