[Clinical follow-up studies on the prognostic significance of immunohistochemical estrogen receptor determination of breast cancer].

We investigated the oestrogen-receptor content (ER-ICA) of 614 tissue samples taken from breast carcinomas (all obtained from patients at the Universitäts-Frauenklinik, Mainz FRG) using immunohistochemical procedures. Since the findings of follow-up studies as well as estimates of survival probability (according to the procedure of Kaplan-Meier) for 334 of the primary breast carcinomas were available, it was possible, to assess the prognostic value of the immunohistochemical results. The percentage of receptor-positive tumour cell nuclei (i.e. the heterogeneity of the tumour), as opposed to the staining intensity, proved to be the most useful criterion of the IRS, whose cut off level was determined as being IRS 1. Regardless of their lymph node status, mammary carcinomas which were immunohistochemically positive for estrogen receptors, were found to have a significantly better short-term prognosis, than breast tumours which were negative for such receptors. In the case of certain breast carcinomas exhibiting contradictory findings (i.e. ER-ICA positive but biochemically negative for oestrogen receptors), the present immunohistochemical method provided the most accurate assessment of the biological behaviour and development of the tumor. Therefore, ER-ICA represents a valuable prognostic criterion, which when complemented with PR-ICA, should facilitate attaining optimal selection of patients suitable for endocrine therapy.