Abstract
Oestrogen receptors were found in 156 (73%) out of 214 primary breast cancers and in 98 (58%) out of 168 metastatic deposits. These proportions reached 82% and 70% respectively in the second half of the study. Receptors were not found in samples of normal breast tissue but small amounts were present in tissue from some hyperplastic lesions and in male gynaecomastia. Receptor concentrations in the malignant samples were evenly distributed over a wide range of values, suggesting that even "negative" tumours might contain trace amounts undetectable by the method used. Each tumour was characterized by a given level of receptor concentration. In most cases the amounts found in the invaded axillary nodes and their corresponding primary tumours were the same. We suggest that quantitative rather than qualitative assessment should provide an appropriate criterion for studies of biochemical and clinical correlations.