Purpose: The study aimed to investigate the expression of thymidine phosphorylase (TP) in renal cell carcinoma (RCC) and its correlation with clinicopathological features and thrombocytosis, and also to determine their prognostic significance. Patients and Methods: TP expression in 127 RCC specimens was evaluated with immunohistochemistry assays. Platelet (PLT) counts of patients before surgery were recorded. Correlations among TP expression, PLT and the clinicopathological features of the patients and their prognostic values were studied statistically. Results: Sixty-eight patients of high TP expression (54%) and 59 of low TP expression (46%) were detected. There were 25 patients with thrombocytosis (20%). High TP expression was significantly associated with tumor stage (p = 0.004), histological grade (p = 0.001) and thrombocytosis (p = 0.012). The 5-year overall survival rate was 88.1% in patients with low TP expression, whereas it was 61.8% in patients with high TP expression (p < 0.001). The 5-year survival rates for patients with and without thrombocytosis were 16.0% and 88.2%, respectively (p < 0.001). The multivariate analysis showed that high TP expression and thrombocytosis would play a role as inde-pendent prognostic factors in RCC patients. Conclusion: High TP expression and thrombocytosis can be regarded as independent prognostic factors of poor survival in patients with RCC. (C) 2016 S. Karger AG, Basel