Clinicopathologic significance of p53 immunostaining in adenocarcinoma of the breast.

Methanol/acetone-fixed frozen sections of 87 breast carcinomas were studied with a panel of three anti-p53 monoclonal antibodies that had specificities for wild-type, mutant, or combined wild-type plus mutant epitopes by using the avidin-biotin method. Nuclear staining was present in 13 (15%) of 87 cases with the mutant-specific antibody. The combined-specificity antibody stained 28 (32%) of 87 cases, including all but one of the tumors that was positive with the mutant-specific antibody. None of the cases reacted with the wild-type-specific antibody. Immunostaining for mutant form p53 was strongly correlated with adverse clinicopathologic factors, including poor differentiation, absence of estrogen receptor protein, nodal metastases, and large tumor size. In groups that were stratified by axillary node status, disease-free survival (52-month mean follow-up) was worse among cases with positive staining for either antibody. This difference was statistically significant in node-positive patients with the combined-specificity antibody (disease free, 22% [p53+] vs recurred, 57% [p53+]). We concluded that (1) immunostaining for mutant forms of p53 characterizes a clinically aggressive subset of breast tumors and may have prognostic utility in some patient populations, and (2) antibody-dependent-staining patterns for p53 may reflect epitope specificities of various mutant forms.