Cancer cell estrogen receptor of human mammary carcinoma.

Estrogen receptor level expressed as percentages of estrogen receptor-positive cancer cells in the infiltrating cancer cell populations was analyzed with a fluorescent estradiol histochemical technique in fifty-two primary infiltrating and metastatic human mammary carcinomas. The estrogen receptor-positive cancer cells equaled or exceeded the estrogen receptor-negative in number in twelve tumors (23%). The remaining (77%) tumors contained largely estrogen receptor-negative cancer cells. Comparison of the estrogen receptor value in the cytosol derived from tumor tissue homogenates with the histochemical finding in forty cases failed to obtain parallel correlation. Noninvasive intraductal carcinomas were found to be consistently composed of estrogen receptor-negative cancer cells even when present in the vicinity of foci of infiltrating cancer cells with high estrogen receptor activity. In contrast, benign intraductal hyperplastic lesions and papillomas were frequently characterized by piling up of estrogen receptor-positive epithelial cells in the mammary ducts. These observations suggest that when malignant transformation takes place, the cancer cells lose most or all of the progenitors' ability to synthesize estrogen receptors during the intraductal stage of proliferation. This ability is only regained, if ever, by some of the cancer cells during the subsequent infiltrating phase in the stroma. Only occasionally, proliferation of the estrogen receptor-positive cancer cells becomes a prevailing tendency in a human mammary cancer.