Mammostrat is a prognostic immunohistochemistry (IHC) test for postmenopausal, node negative, estrogen receptor expressing breast cancer patients who will receive hormonal therapy and are considering adjuvant chemotherapy. Our immunohistochemistry test uses five monoclonal antibody biomarkers and a diagnostic algorithm. The test is used to classify individual patients as having an AGI-defined high-, moderate-, or low-risk of breast cancer recurrence following surgical removal of their primary tumor and treatment with tamoxifen alone. Mammostrat is currently being offered in the United States by AmeriPath's Molecular Profiling Institute (www.molecularprofiling.com). Because Mammostrat uses immunohistochemistry technology, the test can be reimbursed using current Medicare and private insurance categories and requires no special codes.