However, in a Kaplan–Meier analysis stratifying tumours in groups that were either (a) negative for ERα and Mb, (b) positive for ERα or Mb or (c) positive for both ERα and Mb, it became apparent that Mb does add some prognostic information to the ER status (Supplementary Figure S4), as tumours that were either positive for Mb or ER showed an intermediate course in comparison with tumours that were negative or positive for both markers (P=0.001). Here, ESR1 is linked to neoplasm.