Assessment of hormone receptor status in breast cancer by immunohistochemical and gene expression assays

A10 Accurate measurement of hormone receptor expression is critical for the care of breast cancer patients. Immunohistochemical (IHC) assays are currently the most widely used method for hormone receptor determination. While IHC assays have broad utilization there are concerns regarding standardization of methods and interpretation. We assessed hormone receptor status using contemporary estrogen (ER) and progesterone (PR) receptor IHC assays as well as real-time quantitative RT-PCR assays to measure gene expression (GE) levels of ER, PR and additional mRNAs involved in receptor expression.Tumor specimens from 315 well-characterized, early-stage, node-negative breast cancer patients were examined. Although the patients were diagnosed between 1975 and 1986, IHC assays for ER and PR were performed using current methods in a single laboratory. Tumors with an Allred score >3 were classified as positive; those