p53 is a tumor suppressor gene located on the human chromosome 17 that is thought to regulate (suppress) the proliferation of normal cells. The mutant protein accumulates in the nuclei of tumor cells that may then have a proliferative advantage over normal cells. The purpose of this study was to investigate the relationship between levels of mutant p53 expression and the clinical outcome of patients with node-positive and node-negative breast cancer. Expression of mutant p53 was evaluated in 655 human breast carcinomas (349 node-positive and 306 node-negative patients) with long-term clinical follow-up by immunohistochemistry in sections from paraffin embedded tumors.
Results: Immunoreactivity was found in 37.3% of breast tumors. There was no significant correlation between the expression of p53 and tumor size, nodal involvement, age or histological type. However, p53 overexpression was clearly related to histological grade and steroid receptors, with a trend to higher overexpression in ER-tumors or in those with a high histological grade (p < 0.01). On univariate analysis positive tumors were associated with reduced DFS in the total group (p < 0.001) as well as in node-positive patients (p < 0.05) and in node-negative patients (p < 0.01). In conclusion, these results suggest that the immunoreactivity of p53 may be a biologic marker of prognostic significance in both node-positive and node-negative patients.