Increased use of immunohistochemistry for oestrogen receptor measurement in mammary carcinoma: the need for quality assurance.

This paper outlines the changes which have occurred over the last 25 years in the methods employed for the measurement of oestrogen receptors to aid the management of women with breast cancer. Immunohistochemistry is now the method of choice and knowledge of oestrogen receptor status is being used with increasing frequency for the selection of adjuvant treatment as well as for the treatment of metastatic disease. It is essential that good quality assurance procedures are established so that results are reproducible and can be used with confidence in individual centres as well as being comparable with those produced elsewhere. A retrospective study of 170 women with metastatic breast cancer provides the basis for a discussion on the advantages and pitfalls of the immunohistochemical assay. Particular emphasis is paid to the choice of cut-off and how the results may be applied in patient management.