Current Standard Clinical Predictive Markers

In addition to establishing the diagnosis of in situ and/or invasive carcinoma, core needle biopsies of the breast are invaluable for ancillary immunohistochemical and in situ hybridization testing of predictive and prognostic markers in breast cancer, the results of which determine treatment algorithms and options. Whether in the initial diagnostic setting for tumors destined to be routinely surgically excised, or in the setting of tumors to be excised following neoadjuvant therapy or even in the setting of recurrent or metastatic disease, small, well-fixed core needle biopsies of breast are ideally suited for robust, rapid, and reproducible testing. This chapter reviews current standard predictive and prognostic markers in clinical use, with special attention to their utility, guideline recommendations, interpretation, and pitfalls in the setting of core needle biopsies. Specifically, standard estrogen and progesterone receptor testing as well as HER2 testing will be covered in detail. The potential utility of proliferation markers such as Ki67 will also be presented, with a brief examination of the role of proliferation markers in commercially available multigene prognostic assays such as Oncotype DX. Testing of metastatic breast cancer biopsies has also evolved and will be briefly reviewed.