Estrogen receptor immunocytochemistry for preoperative determination of estrogen receptor status on fine-needle aspirates of breast cancer

Fine-needle aspirates (FNAs) of 84 primary breast carcinomas were analyzed immunocytochemically for estrogen receptor (ER) using (ER-ICA) monoclonal antireceptor antibodies. ER-ICA in FNAs was concordant to ER-ICA in histologic biopsies in 87% (P less than 0.0001). In most of the carcinomas, biochemically determined ER status also correlated to ER-ICA. There was no false positive ER-ICA in FNAs compared with ER-ICA in histologic biopsies. In 11 FNAs, ER-ICA was negative, whereas it showed positivity in histologic specimens. The most frequent contributing factors to false negative ER-ICAs of FNAs were ER-ICA-low results in histologic biopsies, a prominent stroma component in these tumors, and low cellularity of FNAs. The biochemical ER values in these cases never exceeded 90 fmol/mg protein. In a minority of cases, false negative results were inexplicable.