Comparative study of the immunohistochemical detection of hormone receptor status and HER-2 expression in primary and paired recurrent/metastatic lesions of patients with breast cancer.

Recent studies have shown some degrees of discordance in ER, PR and HER-2 immunohistochemical expression between primary and recurrent/metastatic lesions (RML). Analysis was made on 78 patients with MBC whose ER, PR and/or HER-2 status were known both on the tissue samples of primary and RML. Among the RML sites, 29.5% were locoregional, 70.5% were distant metastatic sites. Among 75 patients with known ER expression on both primary and RML, 36% (n = 27) showed discordance on ER expression. Among 72 patients with known PR expression on both primary and RML, 54.2% (n = 39) showed discordance on PR expression. Among 61 patients with known HER-2 expression on both primary and RML, 14.7% (n = 9) showed discordance on HER-2 expression. No differences were observed when we compared patients who have discordant ER and HER-2 status with patients who have concordant results between the primary tumor and paired RML with respect to site of biopsy (locoregional vs distant metastasis) and prior therapies (chemotherapy and endocrine therapy). As these discordant results make changes in treatment decision, a biopsy of the metastatic lesion could be recommended in patients with MBC when feasible. Larger series are needed to identify the potential effect of prior therapies and site of metastasis on discordant results.