Objectives: The aim of this project was to search for new risk prognostic markers in the early stage of breast cancer. We tested preoperative plasma transforming growth factor - beta 1 (TGF- beta 1) levels in patients with operable breast cancer. Correlation with traditional prognostic markers and with positivity/negativity sentinel lymph node was evaluated. Materials and Methods: Between 2003 and 2005, 36 patients with operable breast cancer (T1-2, N0-1, M0) with positive or negative sentinel lymph nodes were evaluated for their plasma TGF-beta 1. Twenty-seven healthy individuals (9 premenopausal and 18 postmenopausal) served as controls. Patients were evaluated for the traditional prognostic markers including tumor characteristics, positivity and negativity of sentinel lymph node, TNM, tumor grade, expression of tumor markers CA 15-3 and CEA, hormonal status (pre- or postmenopausal patients, estrogen and progesteron receptor expression), ERB and p53 expression. Predictive value of TGF-beta 1 level and correlation with either of the assessed parameters was tested by one way ANOVA analysis. Results: Measurements of preoperative plasma TGF-beta 1 levels in patients with operable breast cancer were significantly higher compared with healthy individuals (median 15293 and 3983 pg/mL p < 0.0001). TGF-beta 1 level in plasma of patients with a positive sentinel lymph node was significantly higher than in patients with negative sentinel lymph nodes (high vs low, median 18,9 and 14,5 ng/ml, respectively, p = 0.05). Conclusion: The determination of TGF-beta 1 status might help to identify a high-risk population early in tumor progression, for which a more appropriate therapy should be established. In the node-negative population, the up-regulation of TGF-beta 1 might constitute an early event that promotes further progression of breast tumors.