Comparison of five different antibodies in the immunohistochemical assay of estrogen receptor α in human breast cancer

Background Estrogen receptor α(ER) expression is the best prognostic and predictive factor of hormone dependency of human breast cancers. Unlike enzyme immunoassay (EIA), which has been widely used to evaluate ER status in breast cancer, immunohistochemical assay (IHC) can detect ER in a small amounts of tissue with detailed localization. Although there is a sufficient number of ER antibodies against various regions of the protein, the reliability of IHC staining is only well understood for a few. IHC and EIA for the evaluation of the ER status of human breast cancer, therefore, should be compared using the same breast cancer tissues.