ESR2 and ductal breast carcinoma in situ: Immunohistochemical staining for ERβ in normal human breast tissues, DCIS, invasive cancers, and lymph node metastases has revealed a gradual reduction in ERβ expression during the transition from normal tissue to pre-invasive lesions to invasive cancers, with ERβ completely absent in 21% of the invasive cancers studied [40].