The Assessment of Hormone Receptors in Breast Cancer by Immunohistochemistry

There are currently three prognostic/predictive biomarkers used in the routine clinical management of patients with breast cancer, and their assessment is mandatory. They include the estrogen receptor-alpha (ERα), the progesterone receptor (PR), and the erbB2/Her-2 oncogene/oncoprotein. Immunohistochemistry (IHC) is the most commonly used method of assessing these factors, and there are both advantages and persistent problems with using IHC in this setting. Important advantages include the ability to make assessments on routinely available formalin-fixed paraffin-embedded tissue, relatively low cost, and outstanding sensitivity and specificity. Significant problems include inadequate technical standardization and insufficient clinical validation for some of the IHC assays being utilized. This paper briefly reviews the assessment of ERα and PR by IHC in breast cancer, with special emphasis on issues relating to standardization and validation.