Immunostaining of Estrogen Receptors in Paraffin Sections of Breast Cancers Using Anti-Estrophilin Monoclonal Antibodies

Abstract

A monoclonal antibody against estrophilin was used to visualize estrogen receptors in paraffin sections of 59 specimens of primary and metastatic or recurrent breast carcinomas from 28 patients. Immunostaining was carried out with the avidin-biotin technique. Positive staining in the form of brown granules, was seen predominantly in the nucleus of carcinoma cells and less frequently in the cytoplasm. Variations in intensity and extent of the immuno-reactivity was observed in all the sections, among different samples from the same specimens, and among different specimens from the same patients. These staining variations are probably related to heterogeneity of the tumor cell population and suggest the need of examining multiple sections from every specimen and as many specimens as possible from any patient with metastases or recurrences. A good correlation was obtained between immunostaining and receptor content of the corresponding specimens examined by dextran-coated charcoal analysis. About one half of the patients with positively stained tumors responded favorably to anti-estrogen therapy, whereas most of those with negatively stained tumors failed to respond. This study indicates that immunostaining of estrogen receptors in paraffin sections of breast carcinomas is a reliable technique and correlates well with biochemical assays for estrophilin. In this group of patients, positive immunostaining could not be used as a predictor for response to anti-estrogen therapy. On the contrary, negative immunostaining appeared to indicate that the patient was unlikely to benefit from anti-estrogens.