p53 immunohistochemistry in high-grade urothelial carcinoma of the bladder is prognostically significant.

TP53 mutations are characteristic of the high-grade pathway in the dual pathway of urothelial carcinogenesis. These mutations have been correlated with aberrant accumulation of p53 protein; however the definition and significance of this vary in the literature. The aim of this study was to assess p53 immunostaining in a cohort of high-grade urothelial carcinomas by using standard published cut-offs and a novel binarized method that included assessment of the null phenotype. Each scoring method was correlated with oncological outcome. A triplicate core tissue microarray was constructed from 207 cases of high-grade urothelial carcinoma treated by cystectomy, and was stained with p53. The percentage nuclear staining was recorded for each core and averaged for every case (206 cases were evaluable). Cases were categorized as positive/negative according to published cut-offs (10%, 40%) or by binarizing them as abnormal (null phenotype or >50% positivity) and wild type (1-49% positivity). Correlation with disease-specific survival was not significant according to standard definitions of p53 positivity. When a 40% cut-off was used, a correlation with relapse-free survival was significant on univariate analysis (P = 0.038) but not on multivariate analysis (P = 0.079). Abnormal p53 expression showed a near-significant trend for association with disease-specific survival (P = 0.052) and was a significant predictor for relapse-free survival on both univariate analysis (P = 0.047) and multivariate analysis (P = 0.035). Prior to this study, the p53 null phenotype was not well described in urothelial carcinoma of the bladder. Abnormal p53 immunoexpression (null staining pattern or staining in >50% of cells) is prognostic in terms of oncological outcome.