Prediction of endocrine response in breast cancer by immunocytochemical detection of œstrogen receptor in fine-needle aspirates

An immunocytochemical technique has been developed to detect the oestrogen receptor (ER) in samples obtained by fine-needle aspiration of primary or secondary breast carcinoma tissue. 45 (75%) of 60 samples contained sufficient cells for analysis. 19 (90%) of 21 patients who responded to endocrine therapy had samples with ER-positive cells compared with only 7 (39%) of 18 of those who did not respond (p less than 0.001). This test, which causes little pain to the patient and does not need a surgical biopsy, is as accurate as any other method of predicting the response to endocrine treatment in breast cancer.