The localization of 3H-estradiol in estrogen receptor-positive human mammary carcinoma as visualized by thaw-mount autoradiography.

Biochemical assays of human mammary carcinomas for estrogen receptors (ER) are of proven clinical usefulness. The reliability of histochemical or immunocytochemical methods for ER localization are less well established, and less is known about the distribution of estrogen binding proteins in breast cancer. In this report we present results of a study of the uptake and retention of 3H-estradiol after in vitro incubation as visualized by thaw-mount autoradiography in five cases of biochemically estrogen receptor-positive breast cancer. These neoplasms appeared to be composed of a heterogeneous population of labeled and unlabeled tumor cells. The number of nuclear grains varied among putative target cells, and the relative percentage of labeled cells differed from area to area. Non-neoplastic mammary ductal epithelium on occasion revealed significant nuclear labeling, but stromal cells, inflammatory cells, and endothelial cells were generally negative. The possible significance of these findings is discussed.