Advantages of an immunohistochemical estrogen receptor assay

Immunohistochemical and biochemical assays for estrogen and progesterone receptors were done on 20 breast carcinomas, and results were correlated with various histologic features. The slide-based immunohistochemical technique demonstrated several distinct advantages relative to the tissue homogenization required by the traditional biochemical assay. With the use of frozen tissue sections, the immunohistochemical technique permitted direct visualization of antireceptor binding to tumor cells. Receptor staining of reactive stroma, necrotic tumor, and intermingled benign parenchyma was easily distinguished from receptor staining of the actual carcinoma. This separation is not possible with the biochemical assay. In addition, in situ and invasive components and different morphologic subtypes were evaluated independently. Receptor content of the most aggressive portion of the neoplasm is likely to have the greatest clinical relevance and prognostic significance. Careful correlation of histochemical scores with biochemical assay concentrations is needed to permit the application of this technique to patients entering cancer treatment protocols.