Breast cancer is second leading cause of death among women in the United States in 2016 and It is estimated to be responsible for over 40,000 deaths in 2017 (ACS). The use of biomarkers plays a key role in the management of patients with breast cancer, especially in the decision process to select the appropriate systemic therapy to be administered. Furthermore, the discovery of new tissue-based and gene biomarkers has led to the development of a “molecular signature” for predicting patient outcome and treatment modalities. There are three subtypes of breast cancer that are determined by performing specific tests on a sample of the tumor. The first subtype is a tumor that is positive/negative for a hormone receptor, either estrogen (ER) and/or progesterone (PR); tumors without these receptors are classified “hormone receptor-negative”. The second subtype is characterized by the overexpression the human epidermal growth factor receptor 2 (HER2) protein on the tumor. HER2 proteins are receptors on normal breast cells and help control the growth, but when overexpressed make the tumor grow faster and are designated HER2-positive tumors. The last subtype is designated triple-negative, since it does not express ER, PR, and/or HER2.