CLINICOPATHOLOGICAL SIGNIFICANCE OF P53 IMMUNOSTAINING IN ADENOCARCINOMA OF THE BREAST

Methanol/acetone-fixed frozen sections of 87 breast carcinomas were st ained with a panel of three anti-p53 monoclonal antibodies that had sp ecificities for wild-type, mutant, or combined wild-type plus mutant e pitopes by using the avidin-biotin method. Nuclear staining was presen t in 13 (15%) of 87 cases with the mutant-specific antibody. The combi ned-specificity antibody stained 28 (32%) of 87 cases, including all b ut one of the tumors that was positive with the mutant-specific antibo dy. None of the cases reacted with the wild-type-specific antibody. Im munostaining 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 surv ival (52-month mean follow-up) was worse among cases with positive sta ining for either antibody. This difference was statistically significa nt in node-positive patients with the combined-specificity antibody (d isease free, 22% [p53+] vs recurred, 57% [p53+]). We concluded that (1 ) immunostaining for mutant forms of p53 characterizes a clinically ag gressive subset of breast tumors and may have prognostic utility in so me patient populations, and (2) antibody-dependent-staining patterns f or p53 may reflect epitope specificities of various mutant forms.