Pathologic and clinical characteristics of early onset renal cell carcinoma

The majority of renal cell carcinomas (RCCs) occur within the 7th decade of life, uncommonly arising in adults ≤46 years. We reviewed the clinicopathologic features of early onset RCC and evaluated the role of immunohistochemistry (IHC) in potentially identifying diagnoses of newly recognized RCC subtypes that may have been previously misclassified. A retrospective review was performed from 2011-2016 for cases of RCC. Early onset RCC was defined as ≤46 years of age. Clinicopathologic findings and hematoxylin and eosin (H&E) slides were reviewed on early onset RCC patients. IHC was performed on all cases previously diagnosed as unclassified or papillary. Clinicopathologic findings were compared to a control group of RCC patients >46 years over the same time period. We identified 98/598 (16.4%) early onset RCCs. The median age in the early onset RCC and control group was 38.4 and 62.8 years, respectively. The early onset RCC group contained 33/96 (34.3%) females and 63/96 (65.6%) males, including 52/96 (54.2%) whites, 39/96 (40.6%) African Americans, 4/96 (4.2%) Hispanics, and 1/96 (1%) Asian. Nonwhites were significantly more likely to develop early onset RCC (P=.004). Early onset RCCs included 52% clear cell, 28.6% papillary, 8.2% unclassified, 5.1% chromophobe, 3.1% clear cell papillary(CCP), and 3 other rare tumors. Six unclassified and 26 papillary RCCs had tissue available for IHC. Two of 6 (33.3%) unclassified RCCs were reclassified (1 CCP, 1 Xp11 translocation). One of 26 (3.8%) papillary RCCs was reclassified as CCP. Early onset RCCs were more likely to occur in nonwhites (P=.004), be lower stage (P=.03), and undergo partial nephrectomy (P=.002). Few unclassified and papillary tumors were reclassified with IHC.