A greater proportion (above 90%) of tumours in BRCA1 patients are oestrogen receptor-negative than occurs in other breast cancers at the same ages (Lakhani et al, 2005), so there could be a bias towards lower tamoxifen use in ovarian cancer patients than controls, if choice of breast cancer therapy was influenced by oestrogen receptor status. Here, BRCA1 is linked to ovarian carcinoma.