Prognostic significance of KI-67 in renal cell carcinoma: correlation with clinicopathological parameters and survival outcomes

• This study links Ki-67 to RCC prognosis using nuclear grade, dedifferentiation, metastasis, and event-free survival (EFS). • Ki-67 has been associated with tumour grade and dedifferentiation in RCC, supporting its role as a proliferation marker. • Ki-67 lacks independent prognostic value for metastasis or EFS; integrate it into broader multiparametric models. • This article highlights the potential utility of Ki-67 in RCC within a multiparametric prognostic model. Renal cell carcinoma (RCC) is a heterogeneous malignancy with variable clinical behaviour. Ki-67, a nuclear antigen associated with cellular proliferation, has been investigated for its prognostic relevance in RCC. However, its utility in predicting metastatic potential remains controversial, particularly in the Indian population. This study aimed to evaluate Ki-67 expression in RCC and its association with clinicopathological features and metastatic risk. A retrospective analysis of 95 RCC cases was performed at a tertiary care centre between January 2018 and December 2020. Clinicopathological data were retrieved from electronic records, and histological slides were reviewed. Ki-67 immunohistochemistry was performed on tissue microarray (TMA) sections using MIB-1 antibody. The labelling index was calculated, and cases were categorized into low (≤10%) and high (>10%) Ki-67 expression groups. Statistical analysis included chi-square tests, Mann-Whitney U tests, Kruskal-Wallis tests, logistic regression, ROC curve analysis, and Kaplan-Meier survival analysis using SPSS v27. The mean age was 57.09 years; 62.1% were males. Clear cell RCC was the predominant subtype (82.1%). Ki-67 expression was low in 86.3% and high in 13.7% of cases. A higher ISUP grade was significantly associated with increased Ki-67 expression (p = 0.002), and sarcomatoid differentiation correlated with high Ki-67 expression in univariate analysis (OR = 24.3, p = 0.008). However, Ki-67 was not significantly associated with tumour size, stage, or histologic subtype. Metastasis occurred in 13.7% of cases but was not significantly associated with Ki-67 expression (p = 0.49; AUC = 0.438). Event-free survival did not differ significantly between the low and high Ki-67 groups (p = 0.71). Ki-67 showed a significant association with tumour grade and dedifferentiation in RCC, reflecting increased proliferative activity in biologically aggressive tumours. However, Ki-67 lacks independent prognostic value for metastasis or event-free survival, suggesting that Ki-67 should be integrated into a broader multiparametric model rather than used in isolation.