Oestrogen receptor concentration in primary breast cancer and axillary node metastases.

The primary tumour and 1-3 invaded, axillary nodes from each of 24 patients were examined both histologically for the proportion of the specimen constituted by malignant epithelial cells ('cellularity index') and biochemically for oestrogen receptor concentration. Both malignant epithelial cell content and oestrogen receptor concentration were significantly higher in the nodal metastases than in the primary tumours, malignant cells constituting approximately half of the former tissue and three quarters of the latter. On average, receptor concentrations were 1.6 x (protein basis) to 2.3 x (wet weight basis) higher in nodes than in the primary tumours, probably due at least in part to the difference in cellularity. When, to eliminate the effect of the latter, receptor concentration in each tumour deposit was 'corrected' using the appropriate 'cellularity index', the difference in receptor concentration between primary and node was significantly diminished, but not quite eliminated. In one patient, progestogen receptor concentrations were also studied and found to be higher in the nodes than in the primary tumour. If the actual quantity of receptor is to be used for predictive/prognostic purposes, then either a different 'cut-off point' should be used for invaded nodes from that used for assessment on the primary tumour, or receptor concentrations should be corrected for differences in cellularity.