Mesenchymal stromal cells were isolated from the adipose tissue obtained during surgery for breast cancer and cultured under conditions of normal or low oxygen concentrations. In patients that had received a course of radiation and polychemotherapy prior to surgery, the proliferative potential of mesenchymal stromal cells was irreversibly disturbed. In patients receiving no therapy prior to surgery, the morphological, growth, phenotypic, and differentiation characteristics of mesenchymal stromal cells did not differ from the corresponding parameters of mesenchymal stromal cells from healthy donors. Culturing under hypoxic conditions increased adipogenic differentiation potencies of mesenchymal stromal cells from donors and patients.