DNA flow cytometry and the monoclonal antibody DO7 were applied in formalin-fixed, paraffin-embedded specimens from 34 primary male breast carcinomas to verify whether DNA ploidy and p53 expression were associated with survival and proliferative activity. They were compared with tumor clinicopathologic features, sex steroid hormone receptors and cell proliferative activity, assessed by the counts of the argyrophilic nucleolar organizer regions (AgNORs), the monoclonal antibody PC10 against the proliferating cell nuclear antigen and the monoclonal antibody MIB-1. A significant correlation was found between survival and tumor ploidy (median survival, 77 months for diploid but only 38 months for aneuploid cases; P = .03) and p53 expression (median survival, 95 months for cases with p53 scores < or = 14.06% versus 33 for cases with P53 scores > 14.06%; P = .0004; median survival, 99 months for p53 negative vs 39 for positive cases; P = .007). Tumor histological grade (P = .006), AgNOR counts (P = .0001), PC10 scores (P = .002), and MIB-1 scores (P = .001) were also associated with prognosis. In the multivariate analysis, only p53 scores (P = .001) or p53 immunopositivity (P = .003) and AgNOR counts (P = .022) retained an independent prognostic significance. Aneuploid tumors had higher AgNOR counts (P = .002), PC10 (P = .007), MIB-1 (P = .006), and p53 scores (P = .01) than diploid cases. A linear relationship was observed between p53 scores and AgNOR counts (r = .41; P = .014), PC10 (r = .46; P = .005), and MIB-1 scores (r = .44; P = .011). These results indicate that DNA ploidy and p53 expression are associated with survival and cell proliferative activity in male breast carcinoma. Quantitative parameters, such as DNA ploidy, p53 scores, AgNOR counts, PC10, and MIB-1 scores substantially improve the prognostic significance of the traditional parameters in male breast carcinoma.