title: An evaluation of Bosniak's radiological classification of cystic renal masses.
abstract: OBJECTIVE
  To determine the clinical usefulness of Bosniak's classification of cystic renal masses, the differentiation of which remains difficult despite significant advances in diagnostic imaging.
  
  
  METHODS
  The computed tomography (CT) findings of all histopathologically examined cystic renal masses diagnosed at our institution were analysed retrospectively; 35 patients with cystic renal masses were treated between 1986 and 1998. Tissues surgically removed were examined pathologically and the final diagnosis compared with the preoperative CT category of Bosniak's classification.
  
  
  RESULTS
  The histopathological examined showed cystic renal cell carcinoma in 21 patients, a benign renal cyst in 12, haemangiosarcoma in one and transitional cell carcinoma in one. Most of the 35 masses (26, 74%) were found incidentally during evaluation for an unrelated disease or a routine health check. All 11 masses of Bosniak category I were benign and one category II mass was malignant. All 10 masses of category III and 12 of category IV were malignant.
  
  
  CONCLUSIONS
  Bosniak's classification is useful for differentiating category I, III and IV cystic renal masses. There were too few samples to allow meaningful conclusions to be drawn for category II renal masses. It is critical to differentiate between complicated cysts of category II and III because of the major implications for prognosis and clinical management.
authors.affiliation: Departments of Urology, Radiology and Pathology, Nagasaki University School of Medicine, Nagasaki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Koga
authors.forename: M
authors.initials: M
authors.lastname: Nishikido
authors.forename: S
authors.initials: S
authors.lastname: Inuzuka
authors.forename: I
authors.initials: I
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Saito
authors.forename: H
authors.initials: H
authors.lastname: Kanetake
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000145:classification / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000145:classification* / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000145:classification; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed