Multinational study of oestrogen and progesterone receptor immunocytochemistry on breast carcinoma fine needle aspirates.
OBJECTIVES
To collect data on the variability of immunocytochemical (ICC) procedures used to detect oestrogen/progesterone receptors (ER/PR) on cytological material; to test the reproducibility of results; and to identify the crucial points in the ICC procedures that affect the result.


METHODS
Ten laboratories from eight countries participated in a two-part study. In the first part, one of the participants (the coordinator) prepared and distributed cytospins from a fine needle aspirate of a primary breast carcinoma. Laboratories performed ICC staining for ER/PR according to their own methods on the test slides and in-house positive controls. Slides were returned to the coordinator together with information on the preparation of positive control slides and the ICC methodology used. In the second part, obligatory methods of fixation and antigen retrieval were specified. Evaluation of results included grading the number of positive cells, staining intensity, background staining, cytoplasmic staining, sample condition and cellularity. Participants evaluated their own results, which were subsequently evaluated by the coordinator.


RESULTS
There was great variability in the preparation of slides for in-house controls and ICC methodology. The outcome of ICC staining of in-house control slides was excellent in two laboratories, adequate in three, sub-optimal in four and inadequate in one. Only six obtained a positive reaction on the test slides and not all were of a high quality. Results of the second run were greatly improved in terms of cellularity of in-house positive control slides, and scores for the percentage of stained cells and staining intensity of control and test slides. Cytospins and monolayer (ThinPrep(®)) preparations were superior to direct smears; methods of fixation and antigen retrieval were the key points in the staining process.


CONCLUSIONS
Our experience points to the need for guidelines for hormonal receptor determination and external quality control on cytological material, in order for cytological methods to be used in routine clinical practice with a suitable degree of confidence.