Objective: To characterize a large series of renal cell carcinomas (RCCs) in young patients and to compare the data obtained to previously published data. Patients and Methods: A total of 130 RCCs diagnosed in patients <40 years of age were collected from 9 different hospitals in Spain. Cases were re-evaluated following the diagnostic criteria of the 2004 WHO classification of renal tumors. Results: Histologically, tumors were classified as clear cell (50.7%), papillary (8.5%), chromophobe (14.6%), unclassified (16.9%) and clear cell papillary (9.3%) RCCs. Organ-confined disease (OCD) was detected in 83.6% of the cases. Tumor size and Fuhrman’s grade were statistically correlated (Spearman’s ρ = 0.391). CD10 (p = 0.000), CK7 (p = 0.000), CD15 (p = 0.016), CD117 (p = 0.000), 34βE12 cytokeratin (p = 0.034) and e-cadherin (p = 0.000) immunostaining significantly differentiated the five histological categories. Conclusions: OCD was more common in young RCC patients. The clear cell phenotype accounted for only 50% of RCCs in this age group, with an increasing number of chromophobe and unclassified RCCs. Clear cell RCCs with a papillary growth pattern accounted for a significant proportion of the cases.

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