title: Significance of the pseudocapsule on MRI of renal neoplasms and its potential application for local staging: a retrospective study.
abstract: 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.
  
  
  METHODS
  Eighty tumors (73 renal cell carcinomas [RCCs] and seven oncocytomas) were preoperatively evaluated by MRI. MRI findings were 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 images 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%.
  
  
  CONCLUSIONS
  The identification of the pseudocapsule offers an additional value for local staging by MRI. The presence of an intact pseudocapsule is a sign of lack of perinephric fat invasion. It is more likely to predict that the tumor can be removed by partial surgery.
authors.affiliation: University Hospital of Strasbourg, Radiology B Chirugie A, Hopital Civil CHU, 1, place de l'hopital BP 426, Strasbourg, Cedex, France 67091.
authors.forename: Catherine
authors.initials: C
authors.lastname: Roy
authors.forename: Sofiane
authors.initials: S
authors.lastname: El Ghali
authors.forename: Xavier
authors.initials: X
authors.lastname: Buy
authors.forename: Veronique
authors.initials: V
authors.lastname: Lindner
authors.forename: Herve
authors.initials: H
authors.lastname: Lang
authors.forename: Christian
authors.initials: C
authors.lastname: Saussine
authors.forename: Didier
authors.initials: D
authors.lastname: Jacqmin
mesh_terms: D018249:Adenoma, Oxyphilic / Q000473:pathology*; D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity