Immunofluorescent detection of estrogen receptors in breast cancer. Comparison with dextran‐coated charcoal and sucrose gradient assays

Biopsy specimens from 106 women with primary operable, recurrent or metastatic breast cancer were analyzed in a double blind study designed to compare the results of a new fluorescent antibody method for detection of estrogen receptors with estrogen receptors measured biochemically with dextran‐coated charcoal and sucrose gradient assay techniques. Assay results correlated in 89.4% of tumors analyzed, and molecular receptor forms (8S and 4S) were accurately predicted in 94.7% of neoplasms studied. Divergent results most often occurred in specimens sparsely populated with malignant cells. The new technique permitted recognition of possible sources of false negative results such as necrosis, absence of tumor and, on occasion, estrogen bound in vivo. It was possible to analyze by the immunofluorescence method two specimens of insufficient size for biochemical assay.