Immunocytochemical assay for estrogen receptor with monoclonal antibody D753P gamma in routinely processed formaldehyde-fixed breast tissue. Comparison with frozen section assay and with monoclonal antibody H222.

BACKGROUND

Estrogen receptor (ER) immunocytochemical assay (ICA) can be a useful procedure in patients with breast cancer. The authors sought to study the utility of monoclonal antibody D75P3 gamma (D75) in paraffin-embedded sections of breast cancers.

METHODS

Sixty-seven cases of breast cancer were studied by ICA for ER using monoclonal antibody D75 in routinely processed formaldehyde-fixed paraffin-embedded tissue, employing ficin predigestion of sections before application of D75. The results were tabulated using a modified histochemical score (HS). In 59 cases, frozen sections of tumors were also studied with D75. In 40 cases, paraffin-embedded sections were stained with both D75 and monoclonal antibody H222 (which is commercially available). Quantitative biochemical ER assays were performed by the standard dextran-coated charcoal method.

RESULTS

Statistical analysis of the data showed a highly significant correlation (P < 0.0001) between biochemical ER and paraffin-embedded section HS using D75. The results of frozen section assay and paraffin-embedded section assay using D75 were also highly correlated (P < 0.0001). In addition, paraffin-embedded section HS using D75 correlated well with paraffin-embedded section HS using H222 (P < 0.0001). However, D75 HS generally were higher than H222 HS because of the more intense staining with D75, and this difference was statistically significant (P < 0.0001). Assuming that the biochemical ER data were "true," paraffin-embedded section ICA with D75 had a diagnostic sensitivity of 100%, a diagnostic specificity of 70%, a positive predictive value of 89%, and a negative predictive value of 100%. The results of biochemical ER status and paraffin-embedded section D75 ICA ER status agreed in 61 of 67 cases (91%). In all six cases where the ER status differed, the biochemical ER status was negative, and the ER status by ICA with D75 was positive, leading the authors to suspect that some of these cases may have been biochemical false-negative findings.

CONCLUSIONS

It was concluded that ICA for ER with D75 using a 2-minute ficin predigestion of formaldehyde-fixed paraffin-embedded tissue is an acceptable alternative to frozen section ICA. In addition, paraffin-embedded section ICA with D75 is easier to interpret than frozen section ICA, and the results are superior to ICA with H222 on paraffin-embedded sections.