Abstract
Breast cancer is the most frequent gynecological malignancy and the main cause of cancer death in the female population worldwide. One of the most significant challenges in its clinical management is the molecular heterogeneity of malignant breast tumors, which is reflected in the current molecular classification of these entities. In each of these tumor molecular subtypes, distinct genetic alterations are involved, and several intracellular signaling pathways contribute to defining their biological identity and clinical response. This literature review summarized the main classic and emerging biomarkers in breast cancer, along with the therapies associated with them. There are several classic biomarkers associated with this disease, such as estrogen and progesterone receptors, the HER2 receptor, and the Ki-67 cell proliferation marker. Given the limitations of these biomarkers, new biomarkers have been identified, including the TP53 tumor suppressor gene, the EGFR, different types of RNAs, plus epigenetic and immunological biomarkers. The integration of classic and emerging biomarkers along with new therapeutic targets in the clinical practice has promoted a thorough understanding of the high molecular complexity of breast cancer and the development of precision medicine strategies which increase the chances of therapeutic success.