Detection of estrophilin in frozen sections of breast cancers using an estrogen receptor immunocytochemical assay.

Estrogen receptor (ER) was detected in frozen sections of 36 breast carcinomas using an antiestrophilin monoclonal antibody according to an immunocytochemical technique elaborated and made available by Abbott Laboratories in the form of a kit (ER-immunocytochemical assay monoclonal). Immunostaining was confined to the nuclei of the carcinoma cells. In all positive specimens, nuclei with different staining intensities were present in addition to a variable number of unstained nuclei, presumably because of functional heterogeneity. Of the 36 carcinomas, 27 displayed positive immunostaining, 4 had no staining, and in 5 the staining was borderline. All specimens were assayed for ER content by the dextran-coated charcoal (DCC) technique. When the DCC values were compared with the results of immunostaining it was found that 4 tumors were negative and 27 were positive by both techniques, whereas of 5 cases with borderline staining 3 were negative by DCC and 2 had low DCC values. These correlations proved to be highly significant (P much less than 0.001). The number of stained nuclei (extent of staining) related to the DCC status in a significant manner (P less than 0.01), whereas the intensity of staining did not (P greater than 0.10). These results indicate that immunocytochemical visualization of ER using Abbott's "ER-Immunocytochemical Assay Monoclonal" kit is an easy, reproducible, and reliable technique.