BACKGROUND/AIM: Breast cancer is the most common type of cancer among women. Breast infiltrating ductal carcinoma (IDC) is the most common type of breast cancer, approximately 80% of all breast carcinomas. The aim of this study was to analyze the association of tumor size, evaluated after histopathological analysis, with different clinical and biological parameters in IDC. MATERIALS AND METHODS: The study group included 251 women with IDC without axillary lymph node involvement, aged between 27 and 81 years. Analyzed parameters were: age, histological grade, menopausal status, menarche, pregnancy, abortion, breastfeeding, contraceptive use, hormone replacement therapy, estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), Ki-67, p53 and BCL2. RESULTS: Pathological tumor size was between 0.2 and 5.1 cm (1.43±0.86 cm). Tumors in 45 cases exceeded 2 cm, in eight 3 cm and only in one 5 cm. Pathological size was significantly associated with age >70 vs. <50 years (p=0.054), histological grade III vs. I (p=0.0003), positivity for Ki-67 (p=0.0003) and for p53 (p=0.0032). CONCLUSION: Tumor size was significantly associated with age >70 years, histological grade 3 and immunohistochemically-augmented expression of Ki-67 and p53.