Use of monoclonal antibody for assessment of estrogen receptor content in fine-needle aspiration biopsy specimen from patients with breast cancer.

With increasing emphasis on application of fine-needle aspiration biopsy (FNAB) for an earlier detection of breast cancer, there is clearly a need for a method that requires only a small number of tumor cells for hormone receptor analysis. An immunocytochemical assay utilizing monoclonal antiestrophilin antibody and the peroxidase-antiperoxidase technique has been shown to be highly specific and sensitive for the detection of estrogen receptor (ER) in breast cancer tissues. To assess the usefulness of this technique in FNAB, 62 cases of primary, recurrent, and metastatic breast cancers were studied. The findings from the aspirated cells employing estrogen receptor immunocytochemical assay (ER-ICA) were compared with results obtained from cell population of the same tumors following their removal using both cytochemical (ER-ICA) and biochemical (dextran-coated charcoal assay) methods for ER determination. Overall, there was a 92% concordance between biochemical and cytochemical results. This result suggests that anti-ER monoclonal antibody in immunocytochemical analysis is an effective tool in assessment of ER content in breast cancers. The technique can be easily performed at community hospitals and is well suited for specimens of insufficient size for biochemical assay. It may extend the scope of FNAB and make ER studies possible on material unsuitable for biochemical assay from sites other than breast.