IMMUNOHISTOCHEMICAL DETECTION OF PROGESTERONE RECEPTORS IN BREAST INVASIVE DUCTAL CARCINOMAS - A CORRELATIVE STUDY OF 942 CASES

Detection of progesterone receptors (PRs) in breast invasive ductal ca rcinomas (IDCs) helps to predict response to endocrine therapy and pro vides prognostic information on patient outcome. The dextran-coated ch arcoal (DCC) assay is the method of reference for detecting PRs. The i mmunohistochemical (IHC) detection of PRs spares tumor material and al lows visualization of PR positivity in breast tumors. The purpose of t his study was to validate the IHC-PR detection in paraffin-embedded se ctions of breast IDCs by comparing it with the DCC-PR assay. The PgR-I CA (Abbott) antibody was used to detect PR after microwaving tissue se ctions of 942 primary, metastasis-free breast IDCs. Five hundred fifty (58.4%) tumors were IHC-PR positive. The results of the IHC-PR and DC C-PR methods were highly correlated (p < 0.0001 by the X(2) test). By using the DCC assay as the reference method, sensitivity and specifici ty of the IHC assay were 87.2% and 78.1%, respectively, with an 83.2% concordance for the two assays. By univariate analysis, IHC-PR and DCC -PR were highly correlated with patient outcome in the whole group and the node-negative and -positive groups. By multivariate analysis, Sca rff Bloom and Richardson (SBR) grade 3, DCC-PR <15 fmol/mg protein and tumor size >20 mm were independent prognostic factors for dismal surv ival in the node-positive group. In the nodenegative group, IHC-PR <10 % was the only independent prognostic factor for overall survival, fol lowed by SBR grade 3 and tumor size >20 mm for distant metastasis-free and disease-free survival. The IHC-PR assay is a highly specific and sensitive method that provides insightful information on patient outco me in breast IDC.