PURPOSE: All breast cancer (BC) patients with detectable hormone receptors (HR) expression should be offered endocrine therapy (ET). In premenopausal patients, tamoxifen and/or ovarian suppression (OvS)/ablation (OA) may improve disease outcome. Alteration of phosphatase and tensin homolog (PTEN) signaling pathways could be one of the possible mechanisms of resistance to antiestrogen therapy. The purpose of this study was to investigate the association of PTEN protein expression with prognostic factors such as tumor histology and grade, estrogen receptor (ER) and progesterone receptor (PgR) status, human epidermal growth factor receptor 2 (HER2) and disease outcome in premenopausal patients with HR-positive early BCs treated with adjuvant OA. METHODS: We analyzed a group of premenopausal early stages I/II HR-positive BC patients who had undergone radical mastectomy followed only with adjuvant OA by irradiation. ER and PgR contents were determined by classical biochemical dextran-coated charcoal (DCC) method, HER2 status by chromogen in situ hybridization (CISH) analysis and PTEN status by immunohistochemistry (IHC). RESULTS: Sixty-six premenopausal patients included into this analysis were followed for a median of 17 years (range 17-29). Compared to PTEN-positive BCs, PTEN-negative BCs were significantly more frequently associated with lobular tumor histology (p<0.05), higher ER content (p<0.05), and had significantly decreased disease-free survival (DFS) and overall survival (OS) (p<0.01 for both) compared to patients with PTEN-positive BCs. CONCLUSIONS: It seems that PTEN status determined by protein expression may discriminate between subgroups with poor and good prognosis in premenopausal HR-positive BC patients receiving adjuvant OA.