Oestrogen receptor assay of breast cancer by immunocytochemistry of fine needle aspirates.

Sixty-five patients with operable breast cancer were studied to assess the reliability of immunocytochemical analysis of oestrogen receptor (ER-ICA) in specimens obtained by percutaneous fine needle aspiration. Results obtained with the commercially available ER-ICA kit were compared with those obtained by the routine biochemical radioligand assay of oestrogen receptor (ER) on excised tumour specimens. Fifty-two of 65 percutaneous aspirates were evaluable. Of these, thirty-five (67%) were ER positive by the radioligand method. ER-ICA was found to be a reliable method for oestrogen receptor assay, with a high concordance (90.4%) between it and the radioligand essay. The ER-ICA assay had a sensitivity of 89%, specificity of 94%, positive predictive value of 97% and negative predictive value of 80%. ER-ICA assay performed on material obtained by fine-needle aspiration is a reliable method of ER assay. It can replace formal biopsy for patients with inoperable primary tumours or accessible metastases.