Oestrogen and progesterone receptors in primary breast cancer: a population study.

The results of a single centre study on cytoplasmic oestrogen (ER) and progesterone (PR) receptors and their combinations in primary breast cancer of 1957 patients from various parts of Croatia are presented. The frequency of ER+ tumours and tumour mean ER concentration were higher in patients over 50 years of age, while PR frequency and concentration were similar in patients over and under 50. The ER concentration was positively correlated with the age of patients, but the age-related increase in ER concentration appeared between 50 and 70 years of age. The pattern of receptor coexistence was age related. The frequency of ER+PR+ and ER+PR- increased and that of ER-PR+ and ER-PR- tumours decreased with the age of patients. The concentrations of ER and PR were higher in ER+PR+ than in ER+PR- or ER-PR+ tumours, respectively. When the patients were divided into groups under and over 50 years of age these differences appeared only in the latter group, while in the former the concentrations of ER were similar in ER+PR+ and in ER+PR- tumours, and the concentration of PR was higher in ER+PR+ than in ER-PR+ tumours. These data suggest a biological difference between breast cancers with various receptor combinations, as well as a difference in pathogenesis of the receptor negative and positive breast cancer.