Objective To evaluate the concordance of pathologic features in metastatic renal cell carcinoma (RCC) between the primary nephrectomy and metastasectomy specimens. Methods Primary nephrectomy (n = 454) and matched metastasectomy specimens (n = 680) from patients treated between 1970 and 2009 for RCC were re-reviewed by 1 urologic pathologist in a blinded fashion. RCC histologic subtype, grade, coagulative necrosis, and the presence of sarcomatoid differentiation were compared between the primary and the metastatic tumor with kappa statistics. Results Concordance with the primary tumor was observed for subtype in 647 (95%, kappa = 0.71) of the metastases, for grade in 411 (60%, kappa = 0.35), necrosis in 460 (68%, kappa = 0.32), and sarcomatoid differentiation in 643 (95%, kappa = 0.60). Upgrading was observed in 100%, 63%, and 13% of patients with grades 1, 2, and 3 primary tumors, respectively (no patient had a grade 1 metastatic lesion). Metastatic tumors treated with metastasectomy within 30 days of nephrectomy (n = 145) had similar rates of concordant subtype, necrosis, and sarcomatoid differentiation to those undergoing metastasectomy beyond 30 days from nephrectomy (P >.05 for all), but had higher rates of concordant grade (71% vs 58%, P = .003). Pre-metastasectomy exposure to systemic targeted or immunotherapy was not associated with a change in concordance of histopathologic features. Conclusion Among 454 surgically managed metastatic RCC patients, we observed a high degree of concordance for histologic subtype and sarcomatoid differentiation, and varying degrees of discordance for grade and coagulative tumor necrosis, between primary and metastatic tumors. Further investigation is warranted to understand the biologic and therapeutic implications of these observations.
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