Progesterone and oestrogen receptors in human breast cancer.

Receptors for progesterone were found in 27% of 98 human breast tumours, and for oestrogen in 57% of 191 tumours. With one exception, progesterone receptors were found only in tumours which also contained oestrogen receptors. Levels of oestrogen receptor in positive tumours rose significantly with patient age whereas progesterone receptors were unchanged. Progesterone receptor levels were lower in lymph node metastases than in primary tumours, and oestrogen receptor levels were lower in large tumours (greater than 5 cm diameter) compared to small lesions. Receptor levels were not significantly correlated with circulating concentrations of either oestrogen or prolactin. The implications of receptor measurements in assessing hormone responsiveness of breast tumours are discussed.