Is immunohistochemical analysis of oestrogen and progesterone receptors in endometrial carcinoma superior to the radioligand binding assay?

The aim of this study was to evaluate tissue and steroid receptor heterogeneity in endometrial carcinoma specimens as a possible source of discordance between biochemically assayed receptor status and response to endocrine treatment. For this purpose the oestrogen receptor (OR) and progesterone receptor (PR) levels in specimens from 16 endometrial carcinoma patients were analysed on adjacent tissue sections using both a radiochemical and an immunohistochemical assay. With immunohistochemical receptor analysis extensive tissue and tumour cell receptor heterogeneity was observed. Many tumour samples revealed up to 75 per cent contamination with benign tissue. In the majority of cases, evaluation of immunoreactivity in normal tissue elements of the specimen could explain the apparent discordance between semiquantitative immunohistochemical receptor scoring of tumour cells and radiochemical receptor assay. Immunohistochemical analysis of OR and PR in endometrial carcinoma specimens allows a more specific determination of tumour cell receptor content and hence may yield a more accurate prediction of response to endocrine therapy than the biochemical assay.