ESR1 and ductal breast carcinoma in situ: Five out of 13 basal-like DCIS were ESR1 expression positive, however, there was no observable difference in correlation to the basal-like centroid between ESR1 expression positive (n = 5) and ESR1 expression negative (n = 8) basal-like DCIS (P = 0.62, Mann–Whitney U test).