Are histochemical methods for estrogen receptor valid?

Because of the great usefulness of estrogen receptor determinations in selecting therapy for breast cancer patients a number of histochemical and immunohistochemical methods for visualizing bound estrogen in cells and tissue sections have been proposed. We discuss all of these histochemical methods in the light of the known properties of the estrogen receptor and other estrogen binders, and we consider some criteria that must be met if such methods are to be considered valid for receptor. In spite of the great potential value of histochemical methods, we are forced to conclude that, in their present form, none of them are likely as yet to be detecting estrogen receptor.