The differential ERα and ERβ1 expression in ovarian cancer and in different histological types as shown in the present study may help to explain the poor response rate of tamoxifen (10–15%) in ovarian cancer because tamoxifen binds to both ERα and ERβ1 and most clinical studies using tamoxifen therapy included patients with all histotypes [43, 44]. This evidence concerns the gene ESR1 and ovarian carcinoma.