Immunohistochemical analysis of the p53 protein was performed on paraffin sections of tumor tissue from 210 breast cancer patients. All patients had a follow-up period of more than 5 years. Protein expression of p53 was detected in 64 patients (30.5%). There was significant correlation between p53 protein expression and a high histologic grade (grade II vs grade I/II, 49% vs 23.6%, p = 0.0008) and high mitotic index (> or = 10/10 hpf vs < 10/10 hpf, 42.9% vs 19.6%, p = 0.0004), but not with axillary node status, stromal lymphocytic infiltration, or estrogen receptor or progesterone receptor status. We found that p53 protein expression was not a significant factor in predicting 5-year mortality.