Present status of estrogen-receptor cytochemistry and its application in breast cancer research

Estradiol-BSA-FITC is an hydrophilic macromolecular analog used as a cytochemical marker of estrogen-binding sites. Because of the size of the molecule it seems that the reaction must be carried out on fresh-frozen cryostat sections. The freezing technique affects stainability, even as the freezing temperature. Post-fixation is used or not; the influence of various fixatives is variously interpreted. Thawing of the sections influences the intensity and localization of fluorescence. The concentration of E-BSA-FITC in the incubation medium plays a major role in the binding capacity of estrogen-receptors (ER). Fluorescence involves cytoplasm and/or the nucleus. The specificity of labelling on control sections by different methods of inhibition is variously appreciated. The threshold of ER-positivity varies from 10 to 90% of the cells. Standardization of the procedure, if possible, is highly desirable as much as the interpretation rules of the results.