Immunohistochemical and Biochemical Ligand Binding Estrogen Receptor Assays in Breast Cancer and Comparison to the Measured Time

ABSTRACT

BACKGROUND: The estrogen receptor (ER) in breast cancer specimens has traditionally been assessed using a biochemical ligand binding assay (LBA). Recently, the application of an immunohistochemical method (IHC) for formalin-fixed breast carcinoma tissue has greatly increased. Controversy exists over the accuracy of IHC compared with that of LBA in determining ER. METHODS: Breast-carcinoma tissues were obtained from 247 patients. ER was determined within 1 week or at 4 weeks after surgery by using the traditional LBA and by using IHC with monoclonal antibodies. The ER status was assessed with respect to age, size of tumor, and stage according to the two methods. RESULTS: The concordant rate of ER status was 75% between IHC and LBA. IHC-negative/LBA- positive results occurred in 31 cases (13%) and IHC-positive/LBA-negative were observed in 30 cases (12%). ER-positive cases were more common in older patients. The disconcordant rate was much higher in premenopausal females. There was a significantly lower ER positivity in tumors of larger than 5 cm. ER positivity was significantly lower at 4 weeks compared to within 1 week in both methods, but this did not change the concordance rate between the two methods. CONCLUSIONS: The ER-IHC method appears to be a reasonable substitute for a biochemical ligand binding assay. This is based on a 75% concordance of the method as well as on the findings in the disconcordant cases. The appropriate measured time for ER was within 1 week after the cancer tissues were obtained.