Renal Tumors in Young Adults: A Systematic Review and Meta-Analysis of Epidemiology, Clinical Features, Histopathology, and Outcomes Over Two Decades

Background: Renal tumors in young adults are uncommon and less well characterized compared to those in older populations. This systematic review aimed to determine the epidemiology, clinicopathological features, and outcomes of renal tumors in individuals aged 18–45 years. Methods: Original peer-reviewed cohort studies, randomized controlled trials, and systematic reviews published between 2000 and 2024 were included. Databases searched included PubMed, Scopus, and Web of Science, with the last search conducted in February 2025. Risk of bias was assessed using the Newcastle-Ottawa Scale. A total of 19 studies met the inclusion criteria. Meta-analyses were performed using R (v4.3.1) with a random-effects model. Results: The pooled proportion of incidental tumor diagnoses was 41% (95% confidence interval (CI): 12–77%), while symptomatic tumors accounted for 42% (95% CI: 23–64%). Clear cell renal cell carcinoma (RCC) was the most prevalent histologic subtype (54%), followed by papillary (12%) and chromophobe (7%). The pooled mean tumor size was 6.84 cm. Recurrence and mortality rates were 4% and 8%, respectively. Most studies reported 5-year cancer-specific survival exceeding 90% for localized RCC. Nephron-sparing surgery was performed in more than half of the patients, supporting its safety and effectiveness in early-stage disease. Conclusions: Heterogeneity in outcome reporting, small sample sizes in rare subtypes, and possible publication bias were noted. The review supports the importance of early detection, individualized management, and molecular profiling in aggressive subtypes such as Xp11.2 translocation RCC.