Oestrogen receptor and its potential role in breast cancer development.

The first studies of oestrogen receptor (ER) focused on measurements of levels in breast cancers and relationship to hormonal response, but the introduction of antibodies which can be used on fixed tissue has meant that ER can be studied in detail in normal and precancerous tissue. Cloning and sequencing of ER has resulted in more detailed understanding of structure and function, with the identification of variant forms in both tumours and normal, followed by the discovery that ER has two forms, the classical ER-alpha and ER-beta. Analyses of both forms in normal and preneoplastic breast will be important for our understanding of the role of ER in the development of breast cancer and its possible prevention. Copyright 1999 John Wiley & Sons, Ltd.