Comparison of estrogen receptor immunocytochemical assay in frozen and paraffin sections.

Frozen and paraffin sections of 11 breast carcinomas were stained for estrogen receptors (ER) using the same rat monoclonal primary antibody, D75P3, as the marker and alkaline phosphatase as the chromogen-linking enzyme. The results of this staining process were assessed visually and with the microTICAS image analysis system to determine the degree of correlation between frozen and paraffin-embedded tissue. In all specimens, some fraction of the nuclei stained positively. This included two specimens selected for their biochemically negative assay; one of them stained strongly positively with D75P3. The results of quantitative analysis support the visually apparent correlation between the two types of samples in terms of both overall staining pattern and intensity of nuclear staining. Although the conclusions of this pilot study are limited because of the small number of cases, this method of staining establishes the feasibility of representative ER determination in archival paraffin-processed material. The additional information provided by this method is potentially useful in stratifying patients in prospective studies on the basis of the efficacy of hormonal therapy in biochemically ER positive breast tumors.