Application of estrogen receptor immunocytochemical assay to aspirates from mammographically guided fine needle biopsy of nonpalpable breast lesions.

The importance of hormone receptors in the management and prognosis of breast cancer is well established, but difficult to apply to the growing numbers of very small breast cancers being detected. To assess the feasibility of applying estrogen receptor immunocytochemical assay (ER-ICA) to cytologic specimens, we prospectively studied 100 patients who had fine needle aspiration biopsy (FNAB) of mammographically detected nonpalpable breast lesions. All 100 patients also had surgical excision of these nonpalpable lesions immediately after cytologic aspiration. Twenty malignancies were ultimately diagnosed by histology; 17 of them had been cytologically diagnosed. Using specific monoclonal antibody for estrogen receptor, we applied ER-ICA to cytologic preparation of 15 malignant neoplasms with sufficient cellular material available for the assay. Positive immunostaining was demonstrated in nine cases. No ER expression was seen in six cases. Immunocytochemical assay was also done on frozen tissue of the corresponding surgically removed tumors, with 86.6% concordance between the two results. This study is the first to demonstrate that ER-ICA can be effective in assessing hormone receptor content of mammographically directed cytologic aspirates.