Methodology of immunohistological detection of oestrogen receptor in human breast carcinoma in formalin-fixed, paraffin-embedded tissue: a comparison with frozen section methodology.

We describe a method of immunohistochemically assessing estrogen receptor status on routinely processed formalin-fixed tissue, using a commercially available monoclonal antibody (Abbott H222), with pronase predigestion of tissue sections and overnight antibody incubation. The staining was assessed using the H score system. A series of 94 cases of breast cancer were analysed and the results were compared with assessment by oestrogen receptor immunocytochemical assay performed on frozen section. Direct comparison of the paired sets of H scores obtained with frozen tissue and formalin-fixed tissue showed a highly significant correlation of 0.8 (P < 0.001) between the two methods of oestrogen receptor assessment. Chi-squared analysis using H score cut off points of 50 and 100 also showed a similar significant association (P < 0.001). We conclude that this oestrogen receptor method, applicable to formalin-fixed, paraffin-embedded tissue, gives accurate results on routinely fixed tissue and could be used as an alternative to other methods.