Update on Recommendations for Immunohistochemical Testing of Hormone Receptor Status in Breast Cancer

Breast cancer is the most frequent form of cancer in women worldwide.1 Numerous risk factors have been associated with the development of breast cancer including advanced age, personal and family history, reproductive history, and lifestyle factors. Varying histological subtypes of breast cancer have been described, including ductal and lobular carcinomas, each of which may demonstrate both in situ and invasive components. While the inheritance of susceptibility genes is the cause of breast cancer in approximately 12 % of patients, most breast cancers occur sporadically and are not associated with inherited genetic mutations. Mutations of BRCA1/2 genes are found in approximately 3 % of breast cancers.2 In addition to histological subtype, tumor size, and nodal status, numerous prognostic and predictive markers help guide the clinical management of breast cancer patients. Estrogen receptor (ER) and progesterone receptor (PgR) status, which are currently determined mainly by immunohistochemistry, are two of the most important markers. Per the most recent guideline recommendations by the College of American Pathologists (CAP) and American Society of Clinical Oncology (ASCO), ER and PgR status shoul