ESR1 and ductal breast carcinoma in situ: This revealed that the majority of samples largely group together, however Basal-like (as defined by AIMS10) triple negative (TN) DCIS samples, with low expression for ESR1 (ER), PGR (PR) and ERBB2 (Her2) (Fig. 1b), form a distinct cluster away from other DCIS samples, including other non-basal-like TN DCIS samples (Fig. 1a and see Fig. S1 for all sample subtype classifications by patients).