Objective    To investigate the estrogen receptor (ER) isoforms ERα and ERβ expressions and their relationship with clinicopathological parameters in normal breast tissue

benign breast diseases

breast cancer in situ and invasive breast cancer tissue.     Methods    Breast tissue samples were obtained

including normal breast tissue (14 cases)

benign breast diseases (35 cases)

breast cancer in situ (8 cases) and invasive breast cancer (37 cases). Immunohistochemistry was used to measure the expressions of ERα and ERβ in the breast tissues.     Results    The profiles of the ERα and ERβ expressions in normal tissues and the tissues of benign breast diseases were similar. Compared with normal breast tissues and benign breast diseases

ERα protein level was down-regulated in the tissues of breast cancer in situ and invasive breast cancer significantly (P0.01); ERβ protein level was down-regulated in the tissues of invasive breast cancer notably (P0.01); The coexpression of ERα and ERβ was decreased in the tissues of breast cancer in situ and invasive breast cancer remarkably (P0.01).     Conclusion    ERβ may play a role in the human breast cancer probably by modulating ERα activity.