Comparison of standardized immunohistochemical and biochemical assays for estrogen and progesterone receptors in breast carcinoma.

The purpose of this study was to determine estrogen receptor (ER) and progesterone receptor (PR) expression assessed by dextran-coated charcoal method (DCC) and standardized immunohistochemical method (IHC) in a prospective series of 557 primary breast carcinomas, to assess the concordance between the two assays, and to evaluate the association between hormone receptor expression and various clinicopathological parameters. For ER, results of both methods were in agreement in 73.6% of the cases (277 positive, 133 negative), 74 tumors (13.3%) where IHC+/DCC- and 73 (13.1%) were IHC-/DCC+. For PR, concordant results were observed in 72.7% of the cases (201 positive and 204 negative), 127 tumors (22.8%) were IHC+/DCC- and 25 (4.5%) were IHC-/DCC+. Irrespective of the method used, ER and PR positivity showed a strong negative association with tumor grade. ER+ tumors were significantly more common among older patients. With IHC, PR+ cases were more common among tumors of lobular and mucinous type and among node positive tumors. The only parameter that was related to the concordance rate of ER determination by the DCC and IHC method was the age of the patients, with agreement being significantly lower in the group of patients younger than 50 years. On the other hand, discordant PR determination was more often observed in tumors of lower grade, node positive tumors and in tumors of lobular and mucinous type.