Estrogen receptor determination by monoclonal antibody in fine needle aspiration breast cancer cytologies: a marker of hormone response.

A monoclonal antibody (H222) prepared against purified estrogen receptor has been demonstrated to be highly specific and sensitive in an immunohistochemical assay for the detection and quantification of estrogen receptor in human breast carcinoma biopsy specimens. To evaluate the clinical applicability of this assay in cytologic specimens, response to therapy in 12 patients with recurrent breast cancer was correlated with H222 antibody localization in specimens obtained by fine needle aspiration biopsy. All 7 patients with positive H222 responded to hormone therapy (1 complete and 3 partial remissions and 3 stable disease), while 1 of 5 patients with negative H222 responded (1 stable disease). This experience suggests a role for immunohistochemical estrogen receptor determinations in prediction of response to hormonal therapy in patients whose tumor is accessible only to aspiration biopsy. Special care in the handling and interpretation of specimens is essential to optimal application of this method.