ESR1 and neoplasm: Taken together, these findings indicate that CA-A and CA-B have similar ER expression levels (as indicated by the ER IHC score); however, the accessibility of EREs was significantly lower in tumours with CA-B, suggesting that ER + /HER2 − tumours with CA-B are epigenetically different from ER + /HER2 − tumours with CA-A in terms of ER-associated regulatory landscape.