Evaluation of estrogen receptors by immunocytochemistry on fine-needle aspiration biopsy specimens from breast tumors.

The estrogen receptor (ER) content of 31 surgically removed breast tumors (26 duct carcinomas, one lobular carcinoma, one papillary carcinoma, one colloid carcinoma, one duct carcinoma in situ, and one atypical fibroadenoma) was determined by a commercially available immunocytochemical method (Abbott Laboratories, ER-ICA) on cytologic material obtained by fine needle aspiration biopsy (FNAB) of surgical specimens. Immunocytochemical staining of cells by a peroxidase-antiperoxidase technique was evaluated on the basis of the percentage of positive cells and the intensity of staining. An immuno-staining score for cytologic (IS-CYTO) and histologic (IS-HISTO) material was defined and a threshold of positivity determined to facilitate the semi-quantitation of results and the comparison of cases. The results of immunostaining of cytologic material were compared with the evaluation of ER in corresponding tissue samples as determined by the radioligand binding assay using the dextran-coated charcoal procedure (ER-DCC) and by ER-ICA using cryostat sections of frozen tissue. The sensitivity, specificity, predictive value of a positive test, and test efficiency of ER-ICA in cytologic material as compared to ER-DCC was 96%, 83%, 96% and 93%, respectively. The IS-CYTO was significantly correlated with the IS-HISTO in corresponding histologic material (r = 0.72, P less than 0.001). In conclusion, the combination of ER-ICA with FNAB represents a useful new technique for the evaluation of ER which may be applied to small primary tumors, tumor recurrences, and metastases.