title: Multilocular cystic renal cell carcinoma: comparison of imaging and pathologic findings.
abstract: OBJECTIVE
  The purpose of this study was to retrospectively correlate the imaging and pathologic features of multilocular cystic renal cell carcinoma (RCC), a low-grade neoplasm that has an excellent prognosis.
  
  
  METHODS
  Institutional databases were searched for the period between 2001 and 2010 to identify cases of resected renal tumors that had been evaluated with CT or MRI and been analyzed by a uropathologist to confirm the histologic diagnosis of multilocular cystic RCC. The images (nine CT, 14 MRI) were reviewed, and a Bosniak cyst category was assigned.
  
  
  RESULTS
  Of 23 confirmed cases of multilocular cystic RCC, imaging revealed seven lesions were Bosniak category IIF, 13 were category III, and three were category IV. Pathologic examination of the category IIF lesions revealed 99% fluid, 0.001-1% clear cells lining the septum, and 0% fibrosis. The category III lesions were 98-99% fluid, 1-2% clear cells, and 0% fibrosis. The category IV lesions were 20-40% fluid, 1-5% clear cells, and 60-80% fibrosis. The patient demographics were similar across groups. Clinical follow-up showed no evidence of recurrent or metastatic disease.
  
  
  CONCLUSIONS
  Multilocular cystic RCC is a rare cystic lesion of the kidney that is low risk to the patient and benign in behavior. It has a variable imaging pattern, the Bosniak category ranging from IIF to IV. As multilocular cystic RCC lesions increase in complexity on images (higher Bosniak category), there is a corresponding increase in the volume of malignant cells lining the tumor and an increase in the presence of vascularized fibrous tissue. Regardless of the imaging appearance, the behavior of these tumors was benign in this study. Clinicians and radiologists should be aware that when this carcinoma is reported to occur, the patient has an excellent prognosis.
authors.affiliation: Department of Radiology, New York University School of Medicine, 550 First Ave, HW 202, New York, NY 10016, USA. hindmn01@nyumc.org
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Hindman
authors.forename: Morton A
authors.initials: MA
authors.lastname: Bosniak
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Rosenkrantz
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lee-Felker
authors.forename: Jonathan
authors.initials: J
authors.lastname: Melamed
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007472:Iohexol; D052177:Kidney Diseases, Cystic / Q000175:diagnosis* / Q000473:pathology; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives; D008875:Middle Aged; D009942:Organometallic Compounds; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D007472:Iohexol; D008536:Meglumine; D019786:Gadolinium DTPA