The progress in breast cancer therapy results from popularization of mammography screening and starting the treatment at the early stage of disease. Randomized trials involving adjuvant therapy proved the effectiveness of systemic treatment: hormonotherapy combined with chemotherapy. Introduction of systemic treatment improved survival of patients with breast cancer. The progress in the treatment requires the determination of factors that influence the response to the adjuvant therapy. In the case of breast cancer the prognostic factors and predictive factors are known. The conventional prognostic factors include: tumor burden, status of axillary lymph nodes, histological type of the tumor, grade of malignancy, presence of neoplastic cells in blood and lymph vessels. Prognostic factors allow to determine the course of the disease regardless of administered treatment. Important for the choice of the method of treatment and for prognosis are also predictive factors, that point to potential response to planned therapy. Predictive factors include estrogen receptors (ER), progesterone receptors (PgR) and HER2. The development of molecular biology enabled to utilize DNA microarrays in breast cancer research. The analysis of gene expression profiles unraveled two different subtypes of estrogen-dependent tumors: luminal A and luminal B, that differ with respect to gene expression signature and prognosis. In case of breast cancer with negative receptors also two subtypes exist: HER2 subtype and basal-like subtype. They differ with respect to the course of the disease and poor prognosis is observed.