Classification of Histologic Patterns of Pseudocapsular Invasion in Organ-Confined Renal Cell Carcinoma

A standardized histologic definition and classification of the patterns of renal tumor pseudocapsular invasion (RTPI) in renal cell carcinoma (RCC) is not available. We classified RTPI into 2 main histologic patterns: expansive and infiltrative RTPI. Patients with organ-confined RCC and infiltrative RTPI had a greater risk of cancer-specific death and might require stricter postoperative surveillance strategies.A standardized histologic definition and classification of patterns of renal tumor pseudocapsular invasion (RTPI) in renal cell carcinoma (RCC) is not available. The aim of the present study was to propose a classification of RTPI patterns and assess their correlation with other pathologic features and prognosis.The renal tumor pseudocapsule was assessed by 2 expert genitourinary pathologists on the histologic slides of 190 specimens from radical nephrectomy performed for organ-confined (pT1-pT2) RCC. The histologic patterns of RTPI were classified and described. The association between the RTPI patterns and other pathologic features was assessed. The Kaplan-Meier method was used to calculate the survival functions, and Cox regression models were used to assess the predictors of cancer-specific survival.RTPI was classified into 2 main histologic patterns (expansive and infiltrative). Expansive and infiltrative RTPI was observed in 39.5% and 51.6% of cases, respectively. A significant association between the RTPI pattern and Fuhrman grade (P = .006) and RCC histologic subtype (P = .034) was detected. Patients with infiltrative pseudocapsular invasion had significantly poorer 5- and 10-year cancer-specific survival rates than patients with expansive invasion or no invasion (93.6% vs. 98.9% and 84.9% vs. 93%, respectively; P = .039). The presence of infiltrative pseudocapsular invasion was a significant predictor of cancer-specific survival (hazard ratio 4.38, 95% confidence interval 1.04-20.27).An expansive and an infiltrative RTPI pattern can be described. In our study, patients with organ-confined RCC and an infiltrative RTPI pattern had a greater risk of cancer-specific death and might require stricter postoperative surveillance strategies.