Estrogen receptor immunocytochemical assay (ER-ICA) in human endometrium.

An estrogen receptor immunocytochemical assay (ER-ICA) was applied to 15 tissue samples from human endometrium: five proliferative, five secretory, three carcinomas, and two atypical hyperplasias. A monoclonal anti-ER (H 222 SP gamma, Abbott Lab.) and peroxidase antiperoxidase method were applied on frozen sections, 5 micron thick for light microscopy (LM), 100 micron thick for electron microscopy (preembedding). Positive ER staining was quantitated on tissue sections (LM) using a computerized system of image analysis referred to as SAMBA 200 (Thomson TITN). Positive immunostaining was observed in the nuclei of both epithelial and stromal cells in normal and disordered endometrium. SAMBA 200 quantitative analysis permitted an accurate quantification of ER-positive staining. From this preliminary study it is concluded that (a) ER-ICA constitutes a reliable method to study the ER heterogeneous distribution in tissues and the precise intracellular ER localization, which is not feasible by ER biochemical binding assays; (b) SAMBA 200 analysis of the immunostained tissue sections permits an accurate and reproducible method of evaluating the results to quantitate the staining intensity and to determine the percentage of positive cells and the distribution of positive staining of the various tissue structures (glands and stroma).