Estrogen and progesterone receptors in human breast cancer with concomitant assay of plasma 17beta-estradiol, progesterone, and prolactin levels.

The specific estrogen receptor in the cytosol of human breast cancer tissue was assayed in 217 primary cases. The specific progesterone receptor was also assayed in 48 cases as evidence of estrogen action on the tissue. Both receptors were positive in 45.8% of all cases. Plasma 17beta-estradiol and progesterone were assayed concomitantly with these steroid receptors. The higher hormone levels were found in the cases with fewer receptor binding sites. The relationship between 17beta-estradiol levels in tumor cytosol and the number of binding sites was more clearly observed. Plasma prolactin levels, however, showed no correlation with the number of receptor binding sites or the plasma levels of sex steroids. None of these assayed substances had a clear correlation with the histological type of tumor or the clinical stage of the disease.