Objective: To evaluate the usefulness of immunocytochemical staining on breast fine needle aspiration (FNA) cytology as a routine procedure for determination of estrogen (ER) and progesterone (PR) receptor status.
Study design: FNA cytology material from 864 patients was immunostained for ER and PR using Abbott ER/PR-ICA kits. Percentage of stained nuclei, staining intensity and staining pattern was evaluated. In 259 cases comparison with biochemical assay was possible.
Results: Of the cases, 75.6% were ER positive and 65% PR positive, and 61.6% were both ER and PR positive. Approximately 4% of the smears were inconclusive because of scant cellularity. Concordance between the immunostaining and biochemical method was 84% for ER and 71% for PR. Kappa values were 0.61 and 0.4, respectively. Major discrepancies were found in 7.7% of the specimens.
Conclusion: Inconclusive smears due to scant cellularity is a minor problem. Technical difficulties are few, and false negative and positive staining is rarely seen. The results are comparable to those from the biochemical method, and immunostaining of ER/PR on breast cancer FNA cytology smears is useful as a routine procedure for receptor determination.