Abstract
The determination of estrogen receptor (ER) status in primary and metastatic breast tumours has been facilitated by the recent advent of monoclonal antibodies to ER.
The aim of this study was to determine the feasibility of estrogen receptor immunocytochemical assay (ER-ICA) applied to cytologic specimens from primary and metastatic breast tumours.
One hundred and sixty specimens from 133 patients were evaluated by cytologic ER-ICA. Comparison with histologic ERICA was available for 28 of the specimens and with cytosol assay for 27 specimens. Some 101 of the 160 samples were breast lesions of which 87 had a definitive diagnosis of breast carcinoma. Of these, 68% were considered positive for ER. Metastatic breast cancers comprised 59 of the 160 specimens of which 37% were found to be positive for ER.
The predominant staining intensity (SI) of the nuclei of the tumour cells added to the percentage of cells (PC) stained gave an estrogen receptor score (ERS) in both cytologic and histologic specimens. A positive threshold was determined for an ERS >2, equivalent to ER levels greater than 10 fmol/mg of protein.
We observed very good correlation between cytologic ERS and the corresponding cytosol assay values (r = 0.74; p< 0.001; n = 27). The sensitivity was 95% and the specificity 88%. Correlation with histologic ER-ICA was also very high (r = 0.83; p< 0.001; n = 28). We assessed the role of video image analysis (VIA) and did not find any additional advantages in evaluating cytologic ER-ICA.
We conclude that ER-ICA applied to cytologic specimens can provide a reliable indicator of ER status. This may eliminate the need for open biopsy to obtain tissue for ER assay.