The effect of fixation and processing on the sensitivity of oestrogen receptor assay by immunohistochemistry in breast carcinoma

Aims: To investigate the effect of different fixation and processing regimens on the assessment of oestrogen receptor (ER) by immunohistochemistry (IHC). Methods: The ER results for 420 patients from seven different hospitals in which antigen retrieval and IHC were performed centrally were compared. The intensity of ER positivity was assessed semiquantitatively using the Quick score (range 0-7). The scoring profiles of cases from each different source (hospital) were compared to detect differences in the proportion of cases that were negative (Quick score = 0), moderately positive (Quick score = 1-5), and strongly positive (Quick score = 6-7). Results: There were no significant differences (p = 0.3; χ² test) in the proportion of cases in each category. Conclusions: None of the fixation or processing regimens had a significant adverse effect on the sensitivity of the ER assessment performed by automated immunohistochemistry.