BACKGROUND: Progress in breast cancer surgery results in a decreased frequency of mastectomy, in the early phases of cancer replaced by breast conserving therapy (lumpectomy). Increased popularity of breast reconstruction by fat or adipose stem cells (ASC)-enriched fat transfer raised uncertainty about the possible risk of increased cancer recurrence. In vitro studies suggest that locally secreted cytokines and reconstructed local blood vessels may stimulate cancer expansion or cancer de novo induction from glandular tissue remaining after lumpectomy. OBJECTIVES: The purpose of the study was to evaluate the risk of cancer recurrence in breast cancer patients related to the stromal vascular fraction (SVF) augmentation during autologous fat grafting for breast reconstruction. MATERIAL AND METHODS: The tumor recurrence ratio in 56 patients having the breast reconstructed with autologous ASC (transplanted as the subpopulation present in SVF) was compared with the frequency of tumor recurrence in 252 matched patients treated in clinics without subsequent breast reconstruction. Adipose tissue was collected by the Coleman technique and split into 2 portions: one was used for breast reconstruction, the other was enzymatically digested, and isolated cells were used for the augmentation of fat implanted into the breast area. Cancer recurrence in the experimental and matched control group was evaluated following 3-year-long observation time, and the statistical significance of difference in cancer recurrence between the experimental and control group was evaluated. RESULTS: Cancer recurrence in the group of patients treated with ASC-enriched fat for breast reconstruction was 3.7% and did not differ significantly from the control group data (4.13%). No adverse effects of therapy were observed. CONCLUSIONS: Our study does not produce any data suggesting increased cancer risk following breast reconstruction after a mastectomy or a lumpectomy combined with local radiotherapy. It may be concluded that an autologous transplantation of fat augmented with ASC is a safe and efficient procedure. Longer observation time and the observation of larger numbers of patients would be useful for strengthening the conclusion.