Breast Cancer Biomarkers: Challenges in Routine Estrogen Receptor, Progesterone Receptor, and HER2/neu Evaluation.

CONTEXT.—: Evaluation of estrogen receptor (ER), progesterone receptor (PR), and HER2/neu (HER2) biomarkers is standard of care for all cases of newly diagnosed invasive, recurrent, and metastatic breast cancer. Repeat analysis is also performed in select cases per College of American Pathologists/American Society of Clinical Oncology guidelines and other clinical indications. However, in specific scenarios, preanalytic and analytic variables may pose distinct challenges to testing. OBJECTIVE.—: To provide a review of select challenges in the testing of commonly performed breast cancer biomarkers ER, PR, and HER2 and outline best practices for overcoming these challenges. DATA SOURCES.—: Review of College of American Pathologists/American Society of Clinical Oncology recommendations, current literature, and personal experience of the author. CONCLUSIONS.—: Attention must be given to specimen handling to ensure accurate ER, PR, and HER2 biomarker assessment and appropriate management of breast cancer patients.