Significance of the pseudocapsule on MRI of renal neoplasms and its potential application for local staging: A retrospective study

OBJECTIVE. The purpose of our study was to evaluate the role of MRI in Showing a pseudocapsule for local staging of renal tumors. and its potential application to select patients for partial surgery. MATERIALS AND METHODS. Eighty tumors (73 renal cell carcinomas [RCCs] and seven oncocytomas) were preoperatively evaluated by NfR1. NfR1 findings assessed with a special focus on perinephric fat and pseudocapsule. Correlations were performed with pathologic staging after surgery. RESULTS. At pathology, a pseudocapsule was recognized in 79 cases. Twenty-three RCC were staged pT3a (21 clear cell; two papillary). MR image exhibited a pseudocapsule in 90% of cases as a hypointense rim surrounding the tumor on T2-weighted images. MRI findings concerning isolated analysis of the pseudocapsule for differentiating stage T1/T2 from T3a were sensitivity: 86%, 50%; specificity: 95%, 92%; positive predictive value: 95%, 33%: negative predictive value: 88%, 92%; and accuracy: 93%, 89%, for clear cell and papillary types respectively. For stage T3a, with both abnormalities of the pseudocapsule and perirenal fat. results were, for overall RCC sensitivity: 84%; specificity: 95%; positive predictive value: 91%: negative predictive value: 91%; and accuracy: 91%. CONCLUSION. The identification of the pseudocapsule offers an additional value for local staging by MRI. The presence of an intact pseudocapsule is a sip of lack of perinephric fat invasion. It is more likely to predict that the tumor can be removed by partial surgery.