The estrogen receptor test (ERT) uses the estrogen receptor (ER) tumor marker that allows for immunohistochemical techniques to be performed for diagnostic purposes. Immunohistochemistry (IHC) techniques involve the selective identification of antigen proteins by exploiting these antigen-antibody relationships to characterize your analyte of interest. Previously, the ligand binding assay has been used in the determination of ER activity, however this method was limited because of the requirement of large quantities of fresh tissue needed for each assay. IHC serves as a more efficient methods as this technique allows for the morphology of the tissue to be observed in a tumor-specific manner. This increases the practicability of this technique as in many cases, patients’ tissue samples are l