REPRODUCIBILITY OF MEASUREMENTS OF OESTROGEN- RECEPTOR CONCENTRATION IN BREAST CANCER

Summary.-The reproducibility of measurements of oestrogen-receptor activity has been examined in multiple specimens from a rabbit uterus, a rat mammary tumour and human breast tumours. The relationship between receptor concentra-tion and tumour histology has also been investigated in 11 large primary tumours. In the animal tissues, receptor measurements were relatively reproducible (co-efficient of variance: wet wt. basis 16-17%, protein basis 16-21°0) but in human breast tumours receptor activity varied considerably (c.v.: wet wt. basis, 22-125%; protein basis, 28-7200). In addition to these variations in receptor activity within tumours, there was a difference between tumours, as demonstrated by an analysis of variance (P<001). In the 11 primary breast cancers selected for study, the level of receptor activity was related to menopausal status and the tumour content of the specimen. We conclude that the receptor activity detected varies within a tumour and depends upon the tumour content of the biopsy specimen. Predictions based on precise quantita-tion of receptor concentrations may therefore necessitate replicate tumour samplin