Prognosis and tumor grading in bladder urothelial carcinomas with intratumoral grade heterogeneity.

AIMS: Grade heterogeneity is one of the most debated issues in the grading of urothelial carcinomas. The 2022 WHO classification states that approximately one-third of urothelial carcinomas exhibit grade heterogeneity and suggests that the presence of ≥5% high-grade component may justify classification as high-grade. Nevertheless, the need for further evidence was also emphasized. This study aimed to evaluate the prognostic impact of the high-grade component in urothelial carcinomas with grade heterogeneity and to determine a threshold value for high-grade proportion that is clinically meaningful for grading.

METHODS: This retrospective study included 180 cases of non-muscle-invasive urothelial carcinoma with grade heterogeneity, diagnosed between January 2019 and August 2022 on TUR specimens, with available clinical data. Recurrence and survival time were assessed. Cases with >90% high-grade component were excluded.

RESULTS: Recurrence was observed in 26.7% of cases. The two-year survival rate was 73.3%. While no significant association was found between recurrence and the proportion of high-grade component, survival time significantly decreased as the proportion of high-grade component increased. ROC curve analysis identified 27.5% as the cut-off value associated with adverse prognosis.

CONCLUSION: In non-muscle-invasive urothelial carcinomas, the proportion of high-grade component showed a strong association with survival. Together with literature findings, our results suggest that a threshold higher than 5% may be more appropriate for assigning tumors to the high-grade category. Nonetheless, risk stratification incorporating tumor size and extent remains essential for prognostic evaluation.