Immunostaining of estrogen receptor in paraffin sections of breast carcinomas using monoclonal antibody D75P3γ: effects of fixation

Immunostaining of estrogen receptor was carried out on paraffin sections of breast carcinomas using an anti-estrophilin monoclonal antibody (D75P3 gamma) and the avidin-biotin technique. The tumors were fixed in Bouin's solution or in formalin for varying periods of time at room temperature or at 4 degrees C. Best results were obtained following fixation in Bouin's at room temperature or in formalin at 4 degrees C. The staining was localized in the nuclei of carcinoma cells and was heterogeneous in intensity and extent. Prolonged fixation resulted in decreased immunoreactivity and in the appearance of nonspecific cytoplasmic and background staining. The estrogen receptor immunostaining on paraffin sections was found to be in concordance with that on frozen sections (Abbott ER-ICA) and with the steroid-binding assay (dextran-coated charcoal) in over 90% of the cases. This method is of easy and rapid execution and yields reliable and reproducible results.