American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations for Immunohistochemical Testing of Estrogen and Progesterone Receptors in Breast Cancer (Special Article‪)‬

INTRODUCTION In 2008, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) decided to pursue an investigation of whether a guideline for estrogen receptor (ER) and progesterone receptor (PgR) testing would be necessary and beneficial for patients with breast cancer. The two organizations had published a joint guideline on human epidermal growth factor receptor 2 (HER2) testing in 2007. (1,2) A new Expert Panel was convened to address this issue in 2008, and a document reflecting their expert and evidence-based opinions was developed and approved by both organizations. This version of that document is abbreviated from the original approved document, which is available online and includes introductory sections dealing with ER physiology and measurement, history of ER testing, and discussion of the current issues related to ER and PgR testing for patients with breast cancer.