In spite of huge improvements in early diagnostics and therapy in cancer treatment in the last few decades, breast cancer is one of the leading cause of morbidity and mortality in women, due to metastasis. One of the possible cause are stem like cells, often referred as cancer stem cells /CSC), which metastase in bone marrow. Also, one of the important factors which determine the fate of the cell is microenvironment. Therefore, it is of interest to study how microenvironment modifications, especially the oxidative stress modifications, change CSC growth and differentiation.