Estrogen receptor levels in multiple biopsies from patients with breast cancer.

The results of estrogen receptor assays of more than one sample of breast carcinoma in sixty-two patients are reviewed. There was an overall disagreement of 28 per cent between two simultaneous samples, and in the asynchronous group there was a statistically significant difference (p is less than 0.05) in the interval between those who remained positive and those who became negative. As a practical policy, decisions regarding endocrine ablation should be made on contemporary estrogen receptor status rather than on the status of the primary lesion.