['Type-2 diabetes mellitus (DM) is a metabolic disease affecting several million people all over the world. The correlation between DM and malignancies is well established due to the findings of several large population-based studies. However, for endometrial, breast, colorectal, and liver cancers it has also been reported that DM could exert a negative impact on prognosis, causing a significant reduction in cancer-specific survival. A significant correlation with DM has also been demonstrated in renal cell carcinoma (RCC), but the possible prognostic role of DM in this setting has been poorly investigated and remains controversial. This study provides a retrospective analysis of a single-center surgical series with the aim of assessing the features and prognosis of RCC in DM patients.', 'Since 1987 a prospectively compiled database at our institute has collected the data of 1,761 patients who underwent surgery for RCC. All the patients are followed in a specially dedicated out-patient ambulatory. For this study, patients who were taking insulin or oral anti-hyperglycemic drugs before surgery for RCC were considered as DM cases. Their clinical and pathologic features were compared with those of patients without DM. Then, limiting the analysis to non-metastatic patients, the Kaplan-Meier method was used to calculate survival functions and univariable and multivariable Cox regression models addressed time to RCC-related and non RCC-related mortality.', 'The data of 1,604 patients without DM and 157 with DM (prevalence 8.9%) have been analyzed; the latter were more frequently males, older, and with higher co-morbidity and with more asymptomatic, smaller, and low stage neoplasms, though with a higher grading. After a median follow-up time of 53.4 months (IQR 20-97 months), the factors that influenced RCC-related mortality were the presence of symptoms at diagnosis, tumor size, TMN staging, and grading, while those that influenced non-RCC-related mortality were age, gender, and co-morbidities, whereas the presence of DM showed no influence at all. Moreover, in patients without and with DM, progression rate (19.8% vs. 15.1%, P = 0.195) and RCC-related mortality rate (9.6% vs. 5.3%, P = 0.102) were also statistically equivalent.'] Is pre-existing type-2 diabetes an adverse prognostic factor in patients with renal cell carcinoma : a single-center retrospective study?