Prognostic significance of pseudocapsule status in patients with metastatic renal cell carcinoma treated with tyrosine kinase inhibitors

BACKGROUND: We sought to determine whether pseudocapsule (PS) features have prognostic implications in patients with metastatic renal cell carcinoma (mRCC). METHODS: We retrospectively reviewed 231 patients diagnosed with mRCC and treated with tyrosine kinase inhibitors; 188 patients with data available regarding the tumor-parenchyma interfacial PS of the primary tumor were enrolled for analysis. PS status was evaluated as intact (grade 0), merely involved (grade 1), penetrated (grade 2), and absent (grade 3). We applied the Kaplan-Meier method and Cox regression model to assess the survival impact. RESULTS: Of the 188 patients, 19 (10.1%), 61 (32.4%), 96 (51.1%) and 12 (6.4%) had grade 0, 1, 2 and 3 PS, respectively. PS status was significantly associated with histology (P=0.0206), venous tumor embolus (P=0.0511), microvascular invasion (P=0.0108) and microsatellite formation (P=0.0097). Patients without a PS had the worst overall survival (OS), with a 3-year OS rate of 12.7%, whereas the OS rates for grades 0, 1 and 2 were 78.8%, 50.8% and 43.6%, respectively. Adjusted by other variables, grade 3 and grade 2 PS gave rise to a much higher risk of death across the cohort [hazard ratio (HR) =5.217, P=0.0182; HR =3.765, P=0.0281, respectively]. Sarcomatoid change was also an independent factor for OS (HR =2.932, P=0.0075). In contrast, microsatellite formation was not associated with survival in the cohort. CONCLUSIONS: PS status has prognostic implications for OS in metastatic renal cancer. The absence of the PS and sarcomatoid change are two pathological features related to an extremely poor prognosis.